Swagger Docs (General)

Introduction

The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly defined, a consumer can understand and interact with the remote service with a minimal amount of implementation logic.

An OpenAPI definition can then be used by documentation generation tools to display the API, code generation tools to generate servers and clients in various programming languages, testing tools, and many other use cases.

Definitions

OpenAPI Document

A document (or set of documents) that defines or describes an API. An OpenAPI definition uses and conforms to the OpenAPI Specification.

Path Templating

Path templating refers to the usage of template expressions, delimited by curly braces ({}), to mark a section of a URL path as replaceable using path parameters.

Each template expression in the path MUST correspond to a path parameter that is included in the Path Item itself and/or in each of the Path Item's Operations.

Media Types

Media type definitions are spread across several resources. The media type definitions SHOULD be in compliance with RFC6838.

Some examples of possible media type definitions:

  text/plain; charset=utf-8  application/json  application/vnd.github+json  application/vnd.github.v3+json  application/vnd.github.v3.raw+json  application/vnd.github.v3.text+json  application/vnd.github.v3.html+json  application/vnd.github.v3.full+json  application/vnd.github.v3.diff  application/vnd.github.v3.patch

HTTP Status Codes

The HTTP Status Codes are used to indicate the status of the executed operation. The available status codes are defined by RFC7231 and registered status codes are listed in the IANA Status Code Registry.

Specification

Versions

The OpenAPI Specification is versioned using Semantic Versioning 2.0.0 (semver) and follows the semver specification.

The major.minor portion of the semver (for example 3.0) SHALL designate the OAS feature set. Typically, .patch versions address errors in this document, not the feature set. Tooling which supports OAS 3.0 SHOULD be compatible with all OAS 3.0.* versions. The patch version SHOULD NOT be considered by tooling, making no distinction between 3.0.0 and 3.0.1 for example.

Each new minor version of the OpenAPI Specification SHALL allow any OpenAPI document that is valid against any previous minor version of the Specification, within the same major version, to be updated to the new Specification version with equivalent semantics. Such an update MUST only require changing the openapi property to the new minor version.

For example, a valid OpenAPI 3.0.2 document, upon changing its openapi property to 3.1.0, SHALL be a valid OpenAPI 3.1.0 document, semantically equivalent to the original OpenAPI 3.0.2 document. New minor versions of the OpenAPI Specification MUST be written to ensure this form of backward compatibility.

An OpenAPI document compatible with OAS 3.*.* contains a required openapi field which designates the semantic version of the OAS that it uses. (OAS 2.0 documents contain a top-level version field named swagger and value "2.0".)

Format

An OpenAPI document that conforms to the OpenAPI Specification is itself a JSON object, which may be represented either in JSON or YAML format.

For example, if a field has an array value, the JSON array representation will be used:

{   "field": [ 1, 2, 3 ]}

All field names in the specification are case sensitive. This includes all fields that are used as keys in a map, except where explicitly noted that keys are case insensitive.

The schema exposes two types of fields: Fixed fields, which have a declared name, and Patterned fields, which declare a regex pattern for the field name.

Patterned fields MUST have unique names within the containing object.

In order to preserve the ability to round-trip between YAML and JSON formats, YAML version 1.2 is RECOMMENDED along with some additional constraints:

Tags MUST be limited to those allowed by the JSON Schema ruleset.
Keys used in YAML maps MUST be limited to a scalar string, as defined by the YAML Failsafe schema ruleset.

Note: While APIs may be defined by OpenAPI documents in either YAML or JSON format, the API request and response bodies and other content are not required to be JSON or YAML.

Document Structure

An OpenAPI document MAY be made up of a single document or be divided into multiple, connected parts at the discretion of the user. In the latter case, $ref fields MUST be used in the specification to reference those parts as follows from the JSON Schema definitions.

It is RECOMMENDED that the root OpenAPI document be named: openapi.json or openapi.yaml.

Data Types

Primitive data types in the OAS are based on the types supported by the JSON Schema Specification Wright Draft 00. Note that integer as a type is also supported and is defined as a JSON number without a fraction or exponent part. null is not supported as a type (see nullable for an alternative solution). Models are defined using the Schema Object, which is an extended subset of JSON Schema Specification Wright Draft 00.

Primitives have an optional modifier property: format. OAS uses several known formats to define in fine detail the data type being used. However, to support documentation needs, the format property is an open string-valued property, and can have any value. Formats such as "email", "uuid", and so on, MAY be used even though undefined by this specification. Types that are not accompanied by a format property follow the type definition in the JSON Schema. Tools that do not recognize a specific format MAY default back to the type alone, as if the format is not specified.

The formats defined by the OAS are:

type

format

Comments

integer

int32

signed 32 bits

integer

int64

signed 64 bits (a.k.a long)

number

float

number

double

string

byte

base64 encoded characters

string

binary

any sequence of octets

boolean

string

date

As defined by full-date - RFC3339

string

date-time

As defined by date-time - RFC3339

string

password

A hint to UIs to obscure input.

Rich Text Formatting

Throughout the specification description fields are noted as supporting CommonMark markdown formatting. Where OpenAPI tooling renders rich text it MUST support, at a minimum, markdown syntax as described by CommonMark 0.27. Tooling MAY choose to ignore some CommonMark features to address security concerns.

Relative References in URLs

Unless specified otherwise, all properties that are URLs MAY be relative references as defined by RFC3986. Relative references are resolved using the URLs defined in the Server Object as a Base URI.

Relative references used in $ref are processed as per JSON Reference, using the URL of the current document as the base URI. See also the Reference Object.

Schema

In the following description, if a field is not explicitly REQUIRED or described with a MUST or SHALL, it can be considered OPTIONAL.

OpenAPI Object

This is the root document object of the OpenAPI document.

Fixed Fields

Field Name

Type

Description

openapi

string

REQUIRED. This string MUST be the semantic version number of the OpenAPI Specification version that the OpenAPI document uses. The openapi field SHOULD be used by tooling specifications and clients to interpret the OpenAPI document. This is not related to the API info.version string.

info

Info Object

REQUIRED. Provides metadata about the API. The metadata MAY be used by tooling as required.

servers

[Server Object]

An array of Server Objects, which provide connectivity information to a target server. If the servers property is not provided, or is an empty array, the default value would be a Server Object with a url value of /.

paths

Paths Object

REQUIRED. The available paths and operations for the API.

components

Components Object

An element to hold various schemas for the specification.

security

[Security Requirement Object]

A declaration of which security mechanisms can be used across the API. The list of values includes alternative security requirement objects that can be used. Only one of the security requirement objects need to be satisfied to authorize a request. Individual operations can override this definition. To make security optional, an empty security requirement ({}) can be included in the array.

tags

[string]

A list of tags for API documentation control. Tags can be used for logical grouping of operations by resources or any other qualifier.

summary

string

A short summary of what the operation does.

description

string

A verbose explanation of the operation behavior. CommonMark syntax MAY be used for rich text representation.

externalDocs

External Documentation Object

Additional external documentation for this operation.

operationId

string

Unique string used to identify the operation. The id MUST be unique among all operations described in the API. The operationId value is case-sensitive. Tools and libraries MAY use the operationId to uniquely identify an operation, therefore, it is RECOMMENDED to follow common programming naming conventions.

parameters

[Parameter Object | Reference Object]

A list of parameters that are applicable for this operation. If a parameter is already defined at the Path Item, the new definition will override it but can never remove it. The list MUST NOT include duplicated parameters. A unique parameter is defined by a combination of a name and location. The list can use the Reference Object to link to parameters that are defined at the OpenAPI Object's components/parameters.

requestBody

Request Body Object | Reference Object

The request body applicable for this operation. The requestBody is only supported in HTTP methods where the HTTP 1.1 specification RFC7231 has explicitly defined semantics for request bodies. In other cases where the HTTP spec is vague, requestBody SHALL be ignored by consumers.

responses

Responses Object

REQUIRED. The list of possible responses as they are returned from executing this operation.

callbacks

Map[string, Callback Object | Reference Object]

A map of possible out-of band callbacks related to the parent operation. The key is a unique identifier for the Callback Object. Each value in the map is a Callback Object that describes a request that may be initiated by the API provider and the expected responses.

deprecated

boolean

Declares this operation to be deprecated. Consumers SHOULD refrain from usage of the declared operation. Default value is false.

security

[Security Requirement Object]

A declaration of which security mechanisms can be used for this operation. The list of values includes alternative security requirement objects that can be used. Only one of the security requirement objects need to be satisfied to authorize a request. To make security optional, an empty security requirement ({}) can be included in the array. This definition overrides any declared top-level security. To remove a top-level security declaration, an empty array can be used.

servers

[Server Object]

An alternative server array to service this operation. If an alternative server object is specified at the Path Item Object or Root level, it will be overridden by this value.

This object MAY be extended with Specification Extensions.

Operation Object Example

{  "tags": [    "pet"  ],  "summary": "Updates a pet in the store with form data",  "operationId": "updatePetWithForm",  "parameters": [    {      "name": "petId",      "in": "path",      "description": "ID of pet that needs to be updated",      "required": true,      "schema": {        "type": "string"      }    }  ],  "requestBody": {    "content": {      "application/x-www-form-urlencoded": {        "schema": {          "type": "object",          "properties": {            "name": {               "description": "Updated name of the pet",              "type": "string"            },            "status": {              "description": "Updated status of the pet",              "type": "string"            }          },          "required": ["status"]         }      }    }  },  "responses": {    "200": {      "description": "Pet updated.",      "content": {        "application/json": {},        "application/xml": {}      }    },    "405": {      "description": "Method Not Allowed",      "content": {        "application/json": {},        "application/xml": {}      }    }  },  "security": [    {      "petstore_auth": [        "write:pets",        "read:pets"      ]    }  ]}

tags:- petsummary: Updates a pet in the store with form dataoperationId: updatePetWithFormparameters:- name: petId  in: path  description: ID of pet that needs to be updated  required: true  schema:    type: stringrequestBody:  content:    'application/x-www-form-urlencoded':      schema:       properties:          name:             description: Updated name of the pet            type: string          status:            description: Updated status of the pet            type: string       required:         - statusresponses:  '200':    description: Pet updated.    content:       'application/json': {}      'application/xml': {}  '405':    description: Method Not Allowed    content:       'application/json': {}      'application/xml': {}security:- petstore_auth:  - write:pets  - read:pets

External Documentation Object

Allows referencing an external resource for extended documentation.

Fixed Fields

Field Name

Type

Description

description

string

A short description of the target documentation. CommonMark syntax MAY be used for rich text representation.

url

string

REQUIRED. The URL for the target documentation. Value MUST be in the format of a URL.

This object MAY be extended with Specification Extensions.

External Documentation Object Example

{  "description": "Find more info here",  "url": "https://example.com"}

description: Find more info hereurl: https://example.com

Parameter Object

Describes a single operation parameter.

A unique parameter is defined by a combination of a name and location.

Parameter Locations

There are four possible parameter locations specified by the in field:

path - Used together with Path Templating, where the parameter value is actually part of the operation's URL. This does not include the host or base path of the API. For example, in /items/{itemId}, the path parameter is itemId.
query - Parameters that are appended to the URL. For example, in /items?id=###, the query parameter is id.
header - Custom headers that are expected as part of the request. Note that RFC7230 states header names are case insensitive.
cookie - Used to pass a specific cookie value to the API.

Fixed Fields

Field Name

Type

Description

name

string

REQUIRED. The name of the parameter. Parameter names are case sensitive.

If in is "path", the name field MUST correspond to a template expression occurring within the path field in the Paths Object. See Path Templating for further information.
If in is "header" and the name field is "Accept", "Content-Type" or "Authorization", the parameter definition SHALL be ignored.
For all other cases, the name corresponds to the parameter name used by the in property.

string

REQUIRED. The location of the parameter. Possible values are "query", "header", "path" or "cookie".

description

string

A brief description of the parameter. This could contain examples of use. CommonMark syntax MAY be used for rich text representation.

required

boolean

Determines whether this parameter is mandatory. If the parameter location is "path", this property is REQUIRED and its value MUST be true. Otherwise, the property MAY be included and its default value is false.

deprecated

boolean

Specifies that a parameter is deprecated and SHOULD be transitioned out of usage. Default value is false.

allowEmptyValue

boolean

Sets the ability to pass empty-valued parameters. This is valid only for query parameters and allows sending a parameter with an empty value. Default value is false. If style is used, and if behavior is n/a (cannot be serialized), the value of allowEmptyValue SHALL be ignored. Use of this property is NOT RECOMMENDED, as it is likely to be removed in a later revision.

The rules for serialization of the parameter are specified in one of two ways. For simpler scenarios, a schema and style can describe the structure and syntax of the parameter.

Field Name

Type

Description

style

string

Describes how the parameter value will be serialized depending on the type of the parameter value. Default values (based on value of in): for query - form; for path - simple; for header - simple; for cookie - form.

explode

boolean

When this is true, parameter values of type array or object generate separate parameters for each value of the array or key-value pair of the map. For other types of parameters this property has no effect. When style is form, the default value is true. For all other styles, the default value is false.

allowReserved

boolean

Determines whether the parameter value SHOULD allow reserved characters, as defined by RFC3986 :/?#[]@!$&'()*+,;= to be included without percent-encoding. This property only applies to parameters with an in value of query. The default value is false.

schema

Schema Object | Reference Object

The schema defining the type used for the parameter.

example

Any

Example of the parameter's potential value. The example SHOULD match the specified schema and encoding properties if present. The example field is mutually exclusive of the examples field. Furthermore, if referencing a schema that contains an example, the example value SHALL override the example provided by the schema. To represent examples of media types that cannot naturally be represented in JSON or YAML, a string value can contain the example with escaping where necessary.

examples

Map[ string, Example Object | Reference Object]

Examples of the parameter's potential value. Each example SHOULD contain a value in the correct format as specified in the parameter encoding. The examples field is mutually exclusive of the example field. Furthermore, if referencing a schema that contains an example, the examples value SHALL override the example provided by the schema.

For more complex scenarios, the content property can define the media type and schema of the parameter. A parameter MUST contain either a schema property, or a content property, but not both. When example or examples are provided in conjunction with the schema object, the example MUST follow the prescribed serialization strategy for the parameter.

Field Name

Type

Description

content

Map[string, Media Type Object]

A map containing the representations for the parameter. The key is the media type and the value describes it. The map MUST only contain one entry.

Style Values

In order to support common ways of serializing simple parameters, a set of style values are defined.

style

type

in

Comments

matrix

primitive, array, object

path

Path-style parameters defined by RFC6570

label

primitive, array, object

path

Label style parameters defined by RFC6570

form

primitive, array, object

query, cookie

Form style parameters defined by RFC6570. This option replaces collectionFormat with a csv (when explode is false) or multi (when explode is true) value from OpenAPI 2.0.

simple

array

path, header

Simple style parameters defined by RFC6570. This option replaces collectionFormat with a csv value from OpenAPI 2.0.

spaceDelimited

array

query

Space separated array values. This option replaces collectionFormat equal to ssv from OpenAPI 2.0.

pipeDelimited

array

query

Pipe separated array values. This option replaces collectionFormat equal to pipes from OpenAPI 2.0.

deepObject

object

query

Provides a simple way of rendering nested objects using form parameters.

Style Examples

Assume a parameter named color has one of the following values:

   string -> "blue"   array -> ["blue","black","brown"]   object -> { "R": 100, "G": 200, "B": 150 }

The following table shows examples of rendering differences for each value.

style

explode

empty

string

array

object

matrix

false

;color

;color=blue

;color=blue,black,brown

;color=R,100,G,200,B,150

matrix

true

;color

;color=blue

;color=blue;color=black;color=brown

;R=100;G=200;B=150

label

false

.blue

.blue.black.brown

.R.100.G.200.B.150

label

true

.blue

.blue.black.brown

.R=100.G=200.B=150

form

false

color=

color=blue

color=blue,black,brown

color=R,100,G,200,B,150

form

true

color=

color=blue

color=blue&color=black&color=brown

R=100&G=200&B=150

simple

false

n/a

blue

blue,black,brown

R,100,G,200,B,150

simple

true

n/a

blue

blue,black,brown

R=100,G=200,B=150

spaceDelimited

false

n/a

blue%20black%20brown

R%20100%20G%20200%20B%20150

pipeDelimited

false

n/a

blue|black|brown

R|100|G|200|B|150

deepObject

true

n/a

color[R]=100&color[G]=200&color[B]=150

This object MAY be extended with Specification Extensions.

Parameter Object Examples

A header parameter with an array of 64 bit integer numbers:

{  "name": "token",  "in": "header",  "description": "token to be passed as a header",  "required": true,  "schema": {    "type": "array",    "items": {      "type": "integer",      "format": "int64"    }  },  "style": "simple"}

name: tokenin: headerdescription: token to be passed as a headerrequired: trueschema:  type: array  items:    type: integer    format: int64style: simple

A path parameter of a string value:

{  "name": "username",  "in": "path",  "description": "username to fetch",  "required": true,  "schema": {    "type": "string"  }}

name: usernamein: pathdescription: username to fetchrequired: trueschema:  type: string

An optional query parameter of a string value, allowing multiple values by repeating the query parameter:

{  "name": "id",  "in": "query",  "description": "ID of the object to fetch",  "required": false,  "schema": {    "type": "array",    "items": {      "type": "string"    }  },  "style": "form",  "explode": true}

name: idin: querydescription: ID of the object to fetchrequired: falseschema:  type: array  items:    type: stringstyle: formexplode: true

A free-form query parameter, allowing undefined parameters of a specific type:

{  "in": "query",  "name": "freeForm",  "schema": {    "type": "object",    "additionalProperties": {      "type": "integer"    },  },  "style": "form"}

in: queryname: freeFormschema:  type: object  additionalProperties:    type: integerstyle: form

A complex parameter using content to define serialization:

{  "in": "query",  "name": "coordinates",  "content": {    "application/json": {      "schema": {        "type": "object",        "required": [          "lat",          "long"        ],        "properties": {          "lat": {            "type": "number"          },          "long": {            "type": "number"          }        }      }    }  }}

in: queryname: coordinatescontent:  application/json:    schema:      type: object      required:        - lat        - long      properties:        lat:          type: number        long:          type: number

Request Body Object

Describes a single request body.

Fixed Fields

Field Name

Type

Description

description

string

A brief description of the request body. This could contain examples of use. CommonMark syntax MAY be used for rich text representation.

content

Map[string, Media Type Object]

REQUIRED. The content of the request body. The key is a media type or media type range and the value describes it. For requests that match multiple keys, only the most specific key is applicable. e.g. text/plain overrides text/*

required

boolean

Determines if the request body is required in the request. Defaults to false.

This object MAY be extended with Specification Extensions.

Request Body Examples

A request body with a referenced model definition.

{  "description": "user to add to the system",  "content": {    "application/json": {      "schema": {        "$ref": "#/components/schemas/User"      },      "examples": {          "user" : {            "summary": "User Example",             "externalValue": "http://foo.bar/examples/user-example.json"          }         }    },    "application/xml": {      "schema": {        "$ref": "#/components/schemas/User"      },      "examples": {          "user" : {            "summary": "User example in XML",            "externalValue": "http://foo.bar/examples/user-example.xml"          }        }    },    "text/plain": {      "examples": {        "user" : {            "summary": "User example in Plain text",            "externalValue": "http://foo.bar/examples/user-example.txt"         }      }     },    "*/*": {      "examples": {        "user" : {            "summary": "User example in other format",            "externalValue": "http://foo.bar/examples/user-example.whatever"        }      }    }  }}

description: user to add to the systemcontent:   'application/json':    schema:      $ref: '#/components/schemas/User'    examples:      user:        summary: User Example        externalValue: 'http://foo.bar/examples/user-example.json'  'application/xml':    schema:      $ref: '#/components/schemas/User'    examples:      user:        summary: User Example in XML        externalValue: 'http://foo.bar/examples/user-example.xml'  'text/plain':    examples:      user:        summary: User example in text plain format        externalValue: 'http://foo.bar/examples/user-example.txt'  '*/*':    examples:      user:         summary: User example in other format        externalValue: 'http://foo.bar/examples/user-example.whatever'

A body parameter that is an array of string values:

{  "description": "user to add to the system",  "content": {    "text/plain": {      "schema": {        "type": "array",        "items": {          "type": "string"        }      }    }  }}

description: user to add to the systemrequired: truecontent:  text/plain:    schema:      type: array      items:        type: string

Media Type Object

Each Media Type Object provides schema and examples for the media type identified by its key.

Fixed Fields

Field Name

Type

Description

schema

Schema Object | Reference Object

The schema defining the content of the request, response, or parameter.

example

Any

Example of the media type. The example object SHOULD be in the correct format as specified by the media type. The example field is mutually exclusive of the examples field. Furthermore, if referencing a schema which contains an example, the example value SHALL override the example provided by the schema.

examples

Map[ string, Example Object | Reference Object]

Examples of the media type. Each example object SHOULD match the media type and specified schema if present. The examples field is mutually exclusive of the example field. Furthermore, if referencing a schema which contains an example, the examples value SHALL override the example provided by the schema.

encoding

Map[string, Encoding Object]

A map between a property name and its encoding information. The key, being the property name, MUST exist in the schema as a property. The encoding object SHALL only apply to requestBody objects when the media type is multipart or application/x-www-form-urlencoded.

This object MAY be extended with Specification Extensions.

Media Type Examples

{  "application/json": {    "schema": {         "$ref": "#/components/schemas/Pet"    },    "examples": {      "cat" : {        "summary": "An example of a cat",        "value":           {            "name": "Fluffy",            "petType": "Cat",            "color": "White",            "gender": "male",            "breed": "Persian"          }      },      "dog": {        "summary": "An example of a dog with a cat's name",        "value" :  {           "name": "Puma",          "petType": "Dog",          "color": "Black",          "gender": "Female",          "breed": "Mixed"        },      "frog": {          "$ref": "#/components/examples/frog-example"        }      }    }  }}

application/json:   schema:    $ref: "#/components/schemas/Pet"  examples:    cat:      summary: An example of a cat      value:        name: Fluffy        petType: Cat        color: White        gender: male        breed: Persian    dog:      summary: An example of a dog with a cat's name      value:        name: Puma        petType: Dog        color: Black        gender: Female        breed: Mixed    frog:      $ref: "#/components/examples/frog-example"

Considerations for File Uploads

In contrast with the 2.0 specification, file input/output content in OpenAPI is described with the same semantics as any other schema type. Specifically:

# content transferred with base64 encodingschema:  type: string  format: base64

# content transferred in binary (octet-stream):schema:  type: string  format: binary

These examples apply to either input payloads of file uploads or response payloads.

A requestBody for submitting a file in a POST operation may look like the following example:

requestBody:  content:    application/octet-stream:      schema:        # a binary file of any type        type: string        format: binary

In addition, specific media types MAY be specified:

# multiple, specific media types may be specified:requestBody:  content:      # a binary file of type png or jpeg    'image/jpeg':      schema:        type: string        format: binary    'image/png':      schema:        type: string        format: binary

To upload multiple files, a multipart media type MUST be used:

requestBody:  content:    multipart/form-data:      schema:        properties:          # The property name 'file' will be used for all files.          file:            type: array            items:              type: string              format: binary

Support for x-www-form-urlencoded Request Bodies

To submit content using form url encoding via RFC1866, the following definition may be used:

requestBody:  content:    application/x-www-form-urlencoded:      schema:        type: object        properties:          id:            type: string            format: uuid          address:            # complex types are stringified to support RFC 1866            type: object            properties: {}

In this example, the contents in the requestBody MUST be stringified per RFC1866 when passed to the server. In addition, the address field complex object will be stringified.

When passing complex objects in the application/x-www-form-urlencoded content type, the default serialization strategy of such properties is described in the Encoding Object's style property as form.

Special Considerations for multipart Content

It is common to use multipart/form-data as a Content-Type when transferring request bodies to operations. In contrast to 2.0, a schema is REQUIRED to define the input parameters to the operation when using multipart content. This supports complex structures as well as supporting mechanisms for multiple file uploads.

When passing in multipart types, boundaries MAY be used to separate sections of the content being transferred — thus, the following default Content-Types are defined for multipart:

If the property is a primitive, or an array of primitive values, the default Content-Type is text/plain
If the property is complex, or an array of complex values, the default Content-Type is application/json
If the property is a type: string with format: binary or format: base64 (aka a file object), the default Content-Type is application/octet-stream

Examples:

requestBody:  content:    multipart/form-data:      schema:        type: object        properties:          id:            type: string            format: uuid          address:            # default Content-Type for objects is `application/json`            type: object            properties: {}          profileImage:            # default Content-Type for string/binary is `application/octet-stream`            type: string            format: binary          children:            # default Content-Type for arrays is based on the `inner` type (text/plain here)            type: array            items:              type: string          addresses:            # default Content-Type for arrays is based on the `inner` type (object shown, so `application/json` in this example)            type: array            items:              type: '#/components/schemas/Address'

An encoding attribute is introduced to give you control over the serialization of parts of multipart request bodies. This attribute is only applicable to multipart and application/x-www-form-urlencoded request bodies.

Encoding Object

A single encoding definition applied to a single schema property.

Fixed Fields

Field Name

Type

Description

contentType

string

The Content-Type for encoding a specific property. Default value depends on the property type: for string with format being binary – application/octet-stream; for other primitive types – text/plain; for object - application/json; for array – the default is defined based on the inner type. The value can be a specific media type (e.g. application/json), a wildcard media type (e.g. image/*), or a comma-separated list of the two types.

headers

Map[string, Header Object | Reference Object]

A map allowing additional information to be provided as headers, for example Content-Disposition. Content-Type is described separately and SHALL be ignored in this section. This property SHALL be ignored if the request body media type is not a multipart.

style

string

Describes how a specific property value will be serialized depending on its type. See Parameter Object for details on the style property. The behavior follows the same values as query parameters, including default values. This property SHALL be ignored if the request body media type is not application/x-www-form-urlencoded.

explode

boolean

When this is true, property values of type array or object generate separate parameters for each value of the array, or key-value-pair of the map. For other types of properties this property has no effect. When style is form, the default value is true. For all other styles, the default value is false. This property SHALL be ignored if the request body media type is not application/x-www-form-urlencoded.

allowReserved

boolean

Determines whether the parameter value SHOULD allow reserved characters, as defined by RFC3986 :/?#[]@!$&'()*+,;= to be included without percent-encoding. The default value is false. This property SHALL be ignored if the request body media type is not application/x-www-form-urlencoded.

This object MAY be extended with Specification Extensions.

Encoding Object Example

requestBody:  content:    multipart/mixed:      schema:        type: object        properties:          id:            # default is text/plain            type: string            format: uuid          address:            # default is application/json            type: object            properties: {}          historyMetadata:            # need to declare XML format!            description: metadata in XML format            type: object            properties: {}          profileImage:            # default is application/octet-stream, need to declare an image type only!            type: string            format: binary      encoding:        historyMetadata:          # require XML Content-Type in utf-8 encoding          contentType: application/xml; charset=utf-8        profileImage:          # only accept png/jpeg          contentType: image/png, image/jpeg          headers:            X-Rate-Limit-Limit:              description: The number of allowed requests in the current period              schema:                type: integer

Responses Object

A container for the expected responses of an operation. The container maps a HTTP response code to the expected response.

The documentation is not necessarily expected to cover all possible HTTP response codes because they may not be known in advance. However, documentation is expected to cover a successful operation response and any known errors.

The default MAY be used as a default response object for all HTTP codes that are not covered individually by the specification.

The Responses Object MUST contain at least one response code, and it SHOULD be the response for a successful operation call.

Fixed Fields

Field Name

Type

Description

default

Response Object | Reference Object

The documentation of responses other than the ones declared for specific HTTP response codes. Use this field to cover undeclared responses. A Reference Object can link to a response that the OpenAPI Object's components/responses section defines.

Patterned Fields

Field Pattern

Type

Description

HTTP Status Code

Response Object | Reference Object

Any HTTP status code can be used as the property name, but only one property per code, to describe the expected response for that HTTP status code. A Reference Object can link to a response that is defined in the OpenAPI Object's components/responses section. This field MUST be enclosed in quotation marks (for example, "200") for compatibility between JSON and YAML. To define a range of response codes, this field MAY contain the uppercase wildcard character X. For example, 2XX represents all response codes between [200-299]. Only the following range definitions are allowed: 1XX, 2XX, 3XX, 4XX, and 5XX. If a response is defined using an explicit code, the explicit code definition takes precedence over the range definition for that code.

This object MAY be extended with Specification Extensions.

Responses Object Example

A 200 response for a successful operation and a default response for others (implying an error):

{  "200": {    "description": "a pet to be returned",    "content": {      "application/json": {        "schema": {          "$ref": "#/components/schemas/Pet"        }      }    }  },  "default": {    "description": "Unexpected error",    "content": {      "application/json": {        "schema": {          "$ref": "#/components/schemas/ErrorModel"        }      }    }  }}

'200':  description: a pet to be returned  content:     application/json:      schema:        $ref: '#/components/schemas/Pet'default:  description: Unexpected error  content:    application/json:      schema:        $ref: '#/components/schemas/ErrorModel'

Response Object

Describes a single response from an API Operation, including design-time, static links to operations based on the response.

Fixed Fields

Field Name

Type

Description

description

string

REQUIRED. A short description of the response. CommonMark syntax MAY be used for rich text representation.

headers

Map[string, Header Object | Reference Object]

Maps a header name to its definition. RFC7230 states header names are case insensitive. If a response header is defined with the name "Content-Type", it SHALL be ignored.

content

Map[string, Media Type Object]

A map containing descriptions of potential response payloads. The key is a media type or media type range and the value describes it. For responses that match multiple keys, only the most specific key is applicable. e.g. text/plain overrides text/*

links

Map[string, Link Object | Reference Object]

A map of operations links that can be followed from the response. The key of the map is a short name for the link, following the naming constraints of the names for Component Objects.

This object MAY be extended with Specification Extensions.

Response Object Examples

Response of an array of a complex type:

{  "description": "A complex object array response",  "content": {    "application/json": {      "schema": {        "type": "array",        "items": {          "$ref": "#/components/schemas/VeryComplexType"        }      }    }  }}

description: A complex object array responsecontent:   application/json:    schema:       type: array      items:        $ref: '#/components/schemas/VeryComplexType'

Response with a string type:

{  "description": "A simple string response",  "content": {    "text/plain": {      "schema": {        "type": "string"      }    }  }}

description: A simple string responsecontent:  text/plain:    schema:      type: string

Plain text response with headers:

{  "description": "A simple string response",  "content": {    "text/plain": {      "schema": {        "type": "string",        "example": "whoa!"      }    }  },  "headers": {    "X-Rate-Limit-Limit": {      "description": "The number of allowed requests in the current period",      "schema": {        "type": "integer"      }    },    "X-Rate-Limit-Remaining": {      "description": "The number of remaining requests in the current period",      "schema": {        "type": "integer"      }    },    "X-Rate-Limit-Reset": {      "description": "The number of seconds left in the current period",      "schema": {        "type": "integer"      }    }  }}

description: A simple string responsecontent:  text/plain:    schema:      type: string    example: 'whoa!'headers:  X-Rate-Limit-Limit:    description: The number of allowed requests in the current period    schema:      type: integer  X-Rate-Limit-Remaining:    description: The number of remaining requests in the current period    schema:      type: integer  X-Rate-Limit-Reset:    description: The number of seconds left in the current period    schema:      type: integer

Response with no return value:

{  "description": "object created"}

description: object created

Callback Object

A map of possible out-of band callbacks related to the parent operation. Each value in the map is a Path Item Object that describes a set of requests that may be initiated by the API provider and the expected responses. The key value used to identify the path item object is an expression, evaluated at runtime, that identifies a URL to use for the callback operation.

Patterned Fields

Field Pattern

Type

Description

{expression}

Path Item Object

A Path Item Object used to define a callback request and expected responses. A complete example is available.

This object MAY be extended with Specification Extensions.

Key Expression

The key that identifies the Path Item Object is a runtime expression that can be evaluated in the context of a runtime HTTP request/response to identify the URL to be used for the callback request. A simple example might be $request.body#/url. However, using a runtime expression the complete HTTP message can be accessed. This includes accessing any part of a body that a JSON Pointer RFC6901 can reference.

For example, given the following HTTP request:

POST /subscribe/myevent?queryUrl=http://clientdomain.com/stillrunning HTTP/1.1Host: example.orgContent-Type: application/jsonContent-Length: 187{  "failedUrl" : "http://clientdomain.com/failed",  "successUrls" : [    "http://clientdomain.com/fast",    "http://clientdomain.com/medium",    "http://clientdomain.com/slow"  ] }201 CreatedLocation: http://example.org/subscription/1

The following examples show how the various expressions evaluate, assuming the callback operation has a path parameter named eventType and a query parameter named queryUrl.

Expression

Value

$url

http://example.org/subscribe/myevent?queryUrl=http://clientdomain.com/stillrunning

$method

POST

$request.path.eventType

myevent

$request.query.queryUrl

http://clientdomain.com/stillrunning

$request.header.content-Type

application/json

$request.body#/failedUrl

http://clientdomain.com/failed

$request.body#/successUrls/2

http://clientdomain.com/medium

$response.header.Location

http://example.org/subscription/1

Callback Object Examples

The following example uses the user provided queryUrl query string parameter to define the callback URL. This is an example of how to use a callback object to describe a WebHook callback that goes with the subscription operation to enable registering for the WebHook.

myCallback:  '{$request.query.queryUrl}':    post:      requestBody:        description: Callback payload        content:           'application/json':            schema:              $ref: '#/components/schemas/SomePayload'      responses:        '200':          description: callback successfully processed

The following example shows a callback where the server is hard-coded, but the query string parameters are populated from the id and email property in the request body.

transactionCallback:  'http://notificationServer.com?transactionId={$request.body#/id}&email={$request.body#/email}':    post:      requestBody:        description: Callback payload        content:           'application/json':            schema:              $ref: '#/components/schemas/SomePayload'      responses:        '200':          description: callback successfully processed

Example Object

Fixed Fields

Field Name

Type

Description

summary

string

Short description for the example.

description

string

Long description for the example. CommonMark syntax MAY be used for rich text representation.

value

Any

Embedded literal example. The value field and externalValue field are mutually exclusive. To represent examples of media types that cannot naturally represented in JSON or YAML, use a string value to contain the example, escaping where necessary.

externalValue

string

A URL that points to the literal example. This provides the capability to reference examples that cannot easily be included in JSON or YAML documents. The value field and externalValue field are mutually exclusive.

This object MAY be extended with Specification Extensions.

In all cases, the example value is expected to be compatible with the type schema of its associated value. Tooling implementations MAY choose to validate compatibility automatically, and reject the example value(s) if incompatible.

Example Object Examples

In a request body:

requestBody:  content:    'application/json':      schema:        $ref: '#/components/schemas/Address'      examples:         foo:          summary: A foo example          value: {"foo": "bar"}        bar:          summary: A bar example          value: {"bar": "baz"}    'application/xml':      examples:         xmlExample:          summary: This is an example in XML          externalValue: 'http://example.org/examples/address-example.xml'    'text/plain':      examples:        textExample:           summary: This is a text example          externalValue: 'http://foo.bar/examples/address-example.txt'

In a parameter:

parameters:  - name: 'zipCode'    in: 'query'    schema:      type: 'string'      format: 'zip-code'    examples:      zip-example:         $ref: '#/components/examples/zip-example'

In a response:

responses:  '200':    description: your car appointment has been booked    content:       application/json:        schema:          $ref: '#/components/schemas/SuccessResponse'        examples:          confirmation-success:            $ref: '#/components/examples/confirmation-success'

Link Object

The Link object represents a possible design-time link for a response. The presence of a link does not guarantee the caller's ability to successfully invoke it, rather it provides a known relationship and traversal mechanism between responses and other operations.

Unlike dynamic links (i.e. links provided in the response payload), the OAS linking mechanism does not require link information in the runtime response.

For computing links, and providing instructions to execute them, a runtime expression is used for accessing values in an operation and using them as parameters while invoking the linked operation.

Fixed Fields

Field Name

Type

Description

operationRef

string

A relative or absolute URI reference to an OAS operation. This field is mutually exclusive of the operationId field, and MUST point to an Operation Object. Relative operationRef values MAY be used to locate an existing Operation Object in the OpenAPI definition.

operationId

string

The name of an existing, resolvable OAS operation, as defined with a unique operationId. This field is mutually exclusive of the operationRef field.

parameters

Map[string, Any | {expression}]

A map representing parameters to pass to an operation as specified with operationId or identified via operationRef. The key is the parameter name to be used, whereas the value can be a constant or an expression to be evaluated and passed to the linked operation. The parameter name can be qualified using the parameter location [{in}.]{name} for operations that use the same parameter name in different locations (e.g. path.id).

requestBody

Any | {expression}

A literal value or {expression} to use as a request body when calling the target operation.

description

string

A description of the link. CommonMark syntax MAY be used for rich text representation.

server

Server Object

A server object to be used by the target operation.

This object MAY be extended with Specification Extensions.

A linked operation MUST be identified using either an operationRef or operationId. In the case of an operationId, it MUST be unique and resolved in the scope of the OAS document. Because of the potential for name clashes, the operationRef syntax is preferred for specifications with external references.

Examples

Computing a link from a request operation where the $request.path.id is used to pass a request parameter to the linked operation.

paths:  /users/{id}:    parameters:    - name: id      in: path      required: true      description: the user identifier, as userId       schema:        type: string    get:      responses:        '200':          description: the user being returned          content:            application/json:              schema:                type: object                properties:                  uuid: # the unique user id                    type: string                    format: uuid          links:            address:              # the target link operationId              operationId: getUserAddress              parameters:                # get the `id` field from the request path parameter named `id`                userId: $request.path.id  # the path item of the linked operation  /users/{userid}/address:    parameters:    - name: userid      in: path      required: true      description: the user identifier, as userId       schema:        type: string    # linked operation    get:      operationId: getUserAddress      responses:        '200':          description: the user's address

When a runtime expression fails to evaluate, no parameter value is passed to the target operation.

Values from the response body can be used to drive a linked operation.

links:  address:    operationId: getUserAddressByUUID    parameters:      # get the `uuid` field from the `uuid` field in the response body      userUuid: $response.body#/uuid

Clients follow all links at their discretion. Neither permissions, nor the capability to make a successful call to that link, is guaranteed solely by the existence of a relationship.

OperationRef Examples

As references to operationId MAY NOT be possible (the operationId is an optional field in an Operation Object), references MAY also be made through a relative operationRef:

links:  UserRepositories:    # returns array of '#/components/schemas/repository'    operationRef: '#/paths/~12.0~1repositories~1{username}/get'    parameters:      username: $response.body#/username

or an absolute operationRef:

links:  UserRepositories:    # returns array of '#/components/schemas/repository'    operationRef: 'https://na2.gigantic-server.com/#/paths/~12.0~1repositories~1{username}/get'    parameters:      username: $response.body#/username

Note that in the use of operationRef, the escaped forward-slash is necessary when using JSON references.

Runtime Expressions

Runtime expressions allow defining values based on information that will only be available within the HTTP message in an actual API call. This mechanism is used by Link Objects and Callback Objects.

The runtime expression is defined by the following ABNF syntax

      expression = ( "$url" / "$method" / "$statusCode" / "$request." source / "$response." source )      source = ( header-reference / query-reference / path-reference / body-reference )      header-reference = "header." token      query-reference = "query." name        path-reference = "path." name      body-reference = "body" ["#" json-pointer ]      json-pointer    = *( "/" reference-token )      reference-token = *( unescaped / escaped )      unescaped       = %x00-2E / %x30-7D / %x7F-10FFFF         ; %x2F ('/') and %x7E ('~') are excluded from 'unescaped'      escaped         = "~" ( "0" / "1" )        ; representing '~' and '/', respectively      name = *( CHAR )      token = 1*tchar      tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /        "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA

Here, json-pointer is taken from RFC 6901, char from RFC 7159 and token from RFC 7230.

The name identifier is case-sensitive, whereas token is not.

The table below provides examples of runtime expressions and examples of their use in a value:

Examples

Source Location

example expression

notes

HTTP Method

$method

The allowable values for the $method will be those for the HTTP operation.

Requested media type

$request.header.accept

Request parameter

$request.path.id

Request parameters MUST be declared in the parameters section of the parent operation or they cannot be evaluated. This includes request headers.

Request body property

$request.body#/user/uuid

In operations which accept payloads, references may be made to portions of the requestBody or the entire body.

Request URL

$url

Response value

$response.body#/status

In operations which return payloads, references may be made to portions of the response body or the entire body.

Response header

$response.header.Server

Single header values only are available

Runtime expressions preserve the type of the referenced value. Expressions can be embedded into string values by surrounding the expression with {} curly braces.

Header Object

The Header Object follows the structure of the Parameter Object with the following changes:

name MUST NOT be specified, it is given in the corresponding headers map.
in MUST NOT be specified, it is implicitly in header.
All traits that are affected by the location MUST be applicable to a location of header (for example, style).

Header Object Example

A simple header of type integer:

{  "description": "The number of allowed requests in the current period",  "schema": {    "type": "integer"  }}

description: The number of allowed requests in the current periodschema:  type: integer

Tag Object

Adds metadata to a single tag that is used by the Operation Object. It is not mandatory to have a Tag Object per tag defined in the Operation Object instances.

Fixed Fields

Field Name

Type

Description

name

string

REQUIRED. The name of the tag.

description

string

A short description for the tag. CommonMark syntax MAY be used for rich text representation.

externalDocs

External Documentation Object

Additional external documentation for this tag.

This object MAY be extended with Specification Extensions.

Tag Object Example

{	"name": "pet",	"description": "Pets operations"}

name: petdescription: Pets operations

Reference Object

A simple object to allow referencing other components in the specification, internally and externally.

The Reference Object is defined by JSON Reference and follows the same structure, behavior and rules.

For this specification, reference resolution is accomplished as defined by the JSON Reference specification and not by the JSON Schema specification.

Fixed Fields

Field Name

Type

Description

$ref

string

REQUIRED. The reference string.

This object cannot be extended with additional properties and any properties added SHALL be ignored.

Reference Object Example

{	"$ref": "#/components/schemas/Pet"}

$ref: '#/components/schemas/Pet'

Relative Schema Document Example

{  "$ref": "Pet.json"}

$ref: Pet.yaml

Relative Documents With Embedded Schema Example

{  "$ref": "definitions.json#/Pet"}

$ref: definitions.yaml#/Pet

Schema Object

The Schema Object allows the definition of input and output data types. These types can be objects, but also primitives and arrays. This object is an extended subset of the JSON Schema Specification Wright Draft 00.

For more information about the properties, see JSON Schema Core and JSON Schema Validation. Unless stated otherwise, the property definitions follow the JSON Schema.

Properties

The following properties are taken directly from the JSON Schema definition and follow the same specifications:

title
multipleOf
maximum
exclusiveMaximum
minimum
exclusiveMinimum
maxLength
minLength
pattern (This string SHOULD be a valid regular expression, according to the Ecma-262 Edition 5.1 regular expression dialect)
maxItems
minItems
uniqueItems
maxProperties
minProperties
required
enum

The following properties are taken from the JSON Schema definition but their definitions were adjusted to the OpenAPI Specification.

type - Value MUST be a string. Multiple types via an array are not supported.
allOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
oneOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
anyOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
not - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
items - Value MUST be an object and not an array. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema. items MUST be present if the type is array.
properties - Property definitions MUST be a Schema Object and not a standard JSON Schema (inline or referenced).
additionalProperties - Value can be boolean or object. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema. Consistent with JSON Schema, additionalProperties defaults to true.
description - CommonMark syntax MAY be used for rich text representation.
format - See Data Type Formats for further details. While relying on JSON Schema's defined formats, the OAS offers a few additional predefined formats.
default - The default value represents what would be assumed by the consumer of the input as the value of the schema if one is not provided. Unlike JSON Schema, the value MUST conform to the defined type for the Schema Object defined at the same level. For example, if type is string, then default can be "foo" but cannot be 1.

Alternatively, any time a Schema Object can be used, a Reference Object can be used in its place. This allows referencing definitions instead of defining them inline.

Additional properties defined by the JSON Schema specification that are not mentioned here are strictly unsupported.

Other than the JSON Schema subset fields, the following fields MAY be used for further schema documentation:

Fixed Fields

Field Name

Type

Description

nullable

boolean

A true value adds "null" to the allowed type specified by the type keyword, only if type is explicitly defined within the same Schema Object. Other Schema Object constraints retain their defined behavior, and therefore may disallow the use of null as a value. A false value leaves the specified or default type unmodified. The default value is false.

discriminator

Discriminator Object

Adds support for polymorphism. The discriminator is an object name that is used to differentiate between other schemas which may satisfy the payload description. See Composition and Inheritance for more details.

readOnly

boolean

Relevant only for Schema "properties" definitions. Declares the property as "read only". This means that it MAY be sent as part of a response but SHOULD NOT be sent as part of the request. If the property is marked as readOnly being true and is in the required list, the required will take effect on the response only. A property MUST NOT be marked as both readOnly and writeOnly being true. Default value is false.

writeOnly

boolean

Relevant only for Schema "properties" definitions. Declares the property as "write only". Therefore, it MAY be sent as part of a request but SHOULD NOT be sent as part of the response. If the property is marked as writeOnly being true and is in the required list, the required will take effect on the request only. A property MUST NOT be marked as both readOnly and writeOnly being true. Default value is false.

xml

XML Object

This MAY be used only on properties schemas. It has no effect on root schemas. Adds additional metadata to describe the XML representation of this property.

externalDocs

External Documentation Object

Additional external documentation for this schema.

example

Any

A free-form property to include an example of an instance for this schema. To represent examples that cannot be naturally represented in JSON or YAML, a string value can be used to contain the example with escaping where necessary.

deprecated

boolean

Specifies that a schema is deprecated and SHOULD be transitioned out of usage. Default value is false.

This object MAY be extended with Specification Extensions.

Composition and Inheritance (Polymorphism)

The OpenAPI Specification allows combining and extending model definitions using the allOf property of JSON Schema, in effect offering model composition. allOf takes an array of object definitions that are validated independently but together compose a single object.

While composition offers model extensibility, it does not imply a hierarchy between the models. To support polymorphism, the OpenAPI Specification adds the discriminator field. When used, the discriminator will be the name of the property that decides which schema definition validates the structure of the model. As such, the discriminator field MUST be a required field. There are two ways to define the value of a discriminator for an inheriting instance.

Use the schema name.
Override the schema name by overriding the property with a new value. If a new value exists, this takes precedence over the schema name. As such, inline schema definitions, which do not have a given id, cannot be used in polymorphism.

XML Modeling

The xml property allows extra definitions when translating the JSON definition to XML. The XML Object contains additional information about the available options.

Schema Object Examples

Primitive Sample

{  "type": "string",  "format": "email"}

type: stringformat: email

Simple Model

{  "type": "object",  "required": [    "name"  ],  "properties": {    "name": {      "type": "string"    },    "address": {      "$ref": "#/components/schemas/Address"    },    "age": {      "type": "integer",      "format": "int32",      "minimum": 0    }  }}

type: objectrequired:- nameproperties:  name:    type: string  address:    $ref: '#/components/schemas/Address'  age:    type: integer    format: int32    minimum: 0

Model with Map/Dictionary Properties

For a simple string to string mapping:

{  "type": "object",  "additionalProperties": {    "type": "string"  }}

type: objectadditionalProperties:  type: string

For a string to model mapping:

{  "type": "object",  "additionalProperties": {    "$ref": "#/components/schemas/ComplexModel"  }}

type: objectadditionalProperties:  $ref: '#/components/schemas/ComplexModel'

Model with Example

{  "type": "object",  "properties": {    "id": {      "type": "integer",      "format": "int64"    },    "name": {      "type": "string"    }  },  "required": [    "name"  ],  "example": {    "name": "Puma",    "id": 1  }}

type: objectproperties:  id:    type: integer    format: int64  name:    type: stringrequired:- nameexample:  name: Puma  id: 1

Models with Composition

{  "components": {    "schemas": {      "ErrorModel": {        "type": "object",        "required": [          "message",          "code"        ],        "properties": {          "message": {            "type": "string"          },          "code": {            "type": "integer",            "minimum": 100,            "maximum": 600          }        }      },      "ExtendedErrorModel": {        "allOf": [          {            "$ref": "#/components/schemas/ErrorModel"          },          {            "type": "object",            "required": [              "rootCause"            ],            "properties": {              "rootCause": {                "type": "string"              }            }          }        ]      }    }  }}

components:  schemas:    ErrorModel:      type: object      required:      - message      - code      properties:        message:          type: string        code:          type: integer          minimum: 100          maximum: 600    ExtendedErrorModel:      allOf:      - $ref: '#/components/schemas/ErrorModel'      - type: object        required:        - rootCause        properties:          rootCause:            type: string

Models with Polymorphism Support

{  "components": {    "schemas": {      "Pet": {        "type": "object",        "discriminator": {          "propertyName": "petType"        },        "properties": {          "name": {            "type": "string"          },          "petType": {            "type": "string"          }        },        "required": [          "name",          "petType"        ]      },      "Cat": {        "description": "A representation of a cat. Note that `Cat` will be used as the discriminator value.",        "allOf": [          {            "$ref": "#/components/schemas/Pet"          },          {            "type": "object",            "properties": {              "huntingSkill": {                "type": "string",                "description": "The measured skill for hunting",                "default": "lazy",                "enum": [                  "clueless",                  "lazy",                  "adventurous",                  "aggressive"                ]              }            },            "required": [              "huntingSkill"            ]          }        ]      },      "Dog": {        "description": "A representation of a dog. Note that `Dog` will be used as the discriminator value.",        "allOf": [          {            "$ref": "#/components/schemas/Pet"          },          {            "type": "object",            "properties": {              "packSize": {                "type": "integer",                "format": "int32",                "description": "the size of the pack the dog is from",                "default": 0,                "minimum": 0              }            },            "required": [              "packSize"            ]          }        ]      }    }  }}

components:  schemas:    Pet:      type: object      discriminator:        propertyName: petType      properties:        name:          type: string        petType:          type: string      required:      - name      - petType    Cat:  ## "Cat" will be used as the discriminator value      description: A representation of a cat      allOf:      - $ref: '#/components/schemas/Pet'      - type: object        properties:          huntingSkill:            type: string            description: The measured skill for hunting            enum:            - clueless            - lazy            - adventurous            - aggressive        required:        - huntingSkill    Dog:  ## "Dog" will be used as the discriminator value      description: A representation of a dog      allOf:      - $ref: '#/components/schemas/Pet'      - type: object        properties:          packSize:            type: integer            format: int32            description: the size of the pack the dog is from            default: 0            minimum: 0        required:        - packSize

Discriminator Object

When request bodies or response payloads may be one of a number of different schemas, a discriminator object can be used to aid in serialization, deserialization, and validation. The discriminator is a specific object in a schema which is used to inform the consumer of the specification of an alternative schema based on the value associated with it.

When using the discriminator, inline schemas will not be considered.

Fixed Fields

Field Name

Type

Description

propertyName

string

REQUIRED. The name of the property in the payload that will hold the discriminator value.

mapping

Map[string, string]

An object to hold mappings between payload values and schema names or references.

The discriminator object is legal only when using one of the composite keywords oneOf, anyOf, allOf.

In OAS 3.0, a response payload MAY be described to be exactly one of any number of types:

MyResponseType:  oneOf:  - $ref: '#/components/schemas/Cat'  - $ref: '#/components/schemas/Dog'  - $ref: '#/components/schemas/Lizard'

which means the payload MUST, by validation, match exactly one of the schemas described by Cat, Dog, or Lizard. In this case, a discriminator MAY act as a "hint" to shortcut validation and selection of the matching schema which may be a costly operation, depending on the complexity of the schema. We can then describe exactly which field tells us which schema to use:

MyResponseType:  oneOf:  - $ref: '#/components/schemas/Cat'  - $ref: '#/components/schemas/Dog'  - $ref: '#/components/schemas/Lizard'  discriminator:    propertyName: petType

The expectation now is that a property with name petType MUST be present in the response payload, and the value will correspond to the name of a schema defined in the OAS document. Thus the response payload:

{  "id": 12345,  "petType": "Cat"}

Will indicate that the Cat schema be used in conjunction with this payload.

In scenarios where the value of the discriminator field does not match the schema name or implicit mapping is not possible, an optional mapping definition MAY be used:

MyResponseType:  oneOf:  - $ref: '#/components/schemas/Cat'  - $ref: '#/components/schemas/Dog'  - $ref: '#/components/schemas/Lizard'  - $ref: 'https://gigantic-server.com/schemas/Monster/schema.json'  discriminator:    propertyName: petType    mapping:      dog: '#/components/schemas/Dog'      monster: 'https://gigantic-server.com/schemas/Monster/schema.json'

Here the discriminator value of dog will map to the schema #/components/schemas/Dog, rather than the default (implicit) value of Dog. If the discriminator value does not match an implicit or explicit mapping, no schema can be determined and validation SHOULD fail. Mapping keys MUST be string values, but tooling MAY convert response values to strings for comparison.

When used in conjunction with the anyOf construct, the use of the discriminator can avoid ambiguity where multiple schemas may satisfy a single payload.

In both the oneOf and anyOf use cases, all possible schemas MUST be listed explicitly. To avoid redundancy, the discriminator MAY be added to a parent schema definition, and all schemas comprising the parent schema in an allOf construct may be used as an alternate schema.

For example:

components:  schemas:    Pet:      type: object      required:      - petType      properties:        petType:          type: string      discriminator:        propertyName: petType        mapping:          dog: Dog    Cat:      allOf:      - $ref: '#/components/schemas/Pet'      - type: object        # all other properties specific to a `Cat`        properties:          name:            type: string    Dog:      allOf:      - $ref: '#/components/schemas/Pet'      - type: object        # all other properties specific to a `Dog`        properties:          bark:            type: string    Lizard:      allOf:      - $ref: '#/components/schemas/Pet'      - type: object        # all other properties specific to a `Lizard`        properties:          lovesRocks:            type: boolean

a payload like this:

{  "petType": "Cat",  "name": "misty"}

will indicate that the Cat schema be used. Likewise this schema:

{  "petType": "dog",  "bark": "soft"}

will map to Dog because of the definition in the mappings element.

XML Object

A metadata object that allows for more fine-tuned XML model definitions.

When using arrays, XML element names are not inferred (for singular/plural forms) and the name property SHOULD be used to add that information. See examples for expected behavior.

Fixed Fields

Field Name

Type

Description

name

string

Replaces the name of the element/attribute used for the described schema property. When defined within items, it will affect the name of the individual XML elements within the list. When defined alongside type being array (outside the items), it will affect the wrapping element and only if wrapped is true. If wrapped is false, it will be ignored.

namespace

string

The URI of the namespace definition. Value MUST be in the form of an absolute URI.

prefix

string

The prefix to be used for the name.

attribute

boolean

Declares whether the property definition translates to an attribute instead of an element. Default value is false.

wrapped

boolean

MAY be used only for an array definition. Signifies whether the array is wrapped (for example, <books><book/><book/></books>) or unwrapped (<book/><book/>). Default value is false. The definition takes effect only when defined alongside type being array (outside the items).

This object MAY be extended with Specification Extensions.

XML Object Examples

The examples of the XML object definitions are included inside a property definition of a Schema Object with a sample of the XML representation of it.

No XML Element

Basic string property:

{    "animals": {        "type": "string"    }}

animals:  type: string

<animals>...</animals>

Basic string array property (wrapped is false by default):

{    "animals": {        "type": "array",        "items": {            "type": "string"        }    }}

animals:  type: array  items:    type: string

<animals>...</animals><animals>...</animals><animals>...</animals>

XML Name Replacement

{  "animals": {    "type": "string",    "xml": {      "name": "animal"    }  }}

animals:  type: string  xml:    name: animal

<animal>...</animal>

XML Attribute, Prefix and Namespace

In this example, a full model definition is shown.

{  "Person": {    "type": "object",    "properties": {      "id": {        "type": "integer",        "format": "int32",        "xml": {          "attribute": true        }      },      "name": {        "type": "string",        "xml": {          "namespace": "http://example.com/schema/sample",          "prefix": "sample"        }      }    }  }}

Person:  type: object  properties:    id:      type: integer      format: int32      xml:        attribute: true    name:      type: string      xml:        namespace: http://example.com/schema/sample        prefix: sample

<Person id="123">    <sample:name xmlns:sample="http://example.com/schema/sample">example</sample:name></Person>

XML Arrays

Changing the element names:

{  "animals": {    "type": "array",    "items": {      "type": "string",      "xml": {        "name": "animal"      }    }  }}

animals:  type: array  items:    type: string    xml:      name: animal

<animal>value</animal><animal>value</animal>

The external name property has no effect on the XML:

{  "animals": {    "type": "array",    "items": {      "type": "string",      "xml": {        "name": "animal"      }    },    "xml": {      "name": "aliens"    }  }}

animals:  type: array  items:    type: string    xml:      name: animal  xml:    name: aliens

<animal>value</animal><animal>value</animal>

Even when the array is wrapped, if a name is not explicitly defined, the same name will be used both internally and externally:

{  "animals": {    "type": "array",    "items": {      "type": "string"    },    "xml": {      "wrapped": true    }  }}

animals:  type: array  items:    type: string  xml:    wrapped: true

<animals>  <animals>value</animals>  <animals>value</animals></animals>

To overcome the naming problem in the example above, the following definition can be used:

{  "animals": {    "type": "array",    "items": {      "type": "string",      "xml": {        "name": "animal"      }    },    "xml": {      "wrapped": true    }  }}

animals:  type: array  items:    type: string    xml:      name: animal  xml:    wrapped: true

<animals>  <animal>value</animal>  <animal>value</animal></animals>

Affecting both internal and external names:

{  "animals": {    "type": "array",    "items": {      "type": "string",      "xml": {        "name": "animal"      }    },    "xml": {      "name": "aliens",      "wrapped": true    }  }}

animals:  type: array  items:    type: string    xml:      name: animal  xml:    name: aliens    wrapped: true

<aliens>  <animal>value</animal>  <animal>value</animal></aliens>

If we change the external element but not the internal ones:

{  "animals": {    "type": "array",    "items": {      "type": "string"    },    "xml": {      "name": "aliens",      "wrapped": true    }  }}

animals:  type: array  items:    type: string  xml:    name: aliens    wrapped: true

<aliens>  <aliens>value</aliens>  <aliens>value</aliens></aliens>

Security Scheme Object

Defines a security scheme that can be used by the operations. Supported schemes are HTTP authentication, an API key (either as a header, a cookie parameter or as a query parameter), OAuth2's common flows (implicit, password, client credentials and authorization code) as defined in RFC6749, and OpenID Connect Discovery.

Fixed Fields

Field Name

Type

Applies To

Description

type

string

Any

REQUIRED. The type of the security scheme. Valid values are "apiKey", "http", "oauth2", "openIdConnect".

description

string

Any

A short description for security scheme. CommonMark syntax MAY be used for rich text representation.

name

string

apiKey

REQUIRED. The name of the header, query or cookie parameter to be used.

string

apiKey

REQUIRED. The location of the API key. Valid values are "query", "header" or "cookie".

scheme

string

http

REQUIRED. The name of the HTTP Authorization scheme to be used in the Authorization header as defined in RFC7235. The values used SHOULD be registered in the IANA Authentication Scheme registry.

bearerFormat

string

http ("bearer")

A hint to the client to identify how the bearer token is formatted. Bearer tokens are usually generated by an authorization server, so this information is primarily for documentation purposes.

flows

OAuth Flows Object

oauth2

REQUIRED. An object containing configuration information for the flow types supported.

openIdConnectUrl

string

openIdConnect

REQUIRED. OpenId Connect URL to discover OAuth2 configuration values. This MUST be in the form of a URL.

This object MAY be extended with Specification Extensions.

Security Scheme Object Example

Basic Authentication Sample

{  "type": "http",  "scheme": "basic"}

type: httpscheme: basic

API Key Sample

{  "type": "apiKey",  "name": "api_key",  "in": "header"}

type: apiKeyname: api_keyin: header

JWT Bearer Sample

{  "type": "http",  "scheme": "bearer",  "bearerFormat": "JWT",}

type: httpscheme: bearerbearerFormat: JWT

Implicit OAuth2 Sample

{  "type": "oauth2",  "flows": {    "implicit": {      "authorizationUrl": "https://example.com/api/oauth/dialog",      "scopes": {        "write:pets": "modify pets in your account",        "read:pets": "read your pets"      }    }  }}

type: oauth2flows:   implicit:    authorizationUrl: https://example.com/api/oauth/dialog    scopes:      write:pets: modify pets in your account      read:pets: read your pets

OAuth Flows Object

Allows configuration of the supported OAuth Flows.

Fixed Fields

Field Name

Type

Description

implicit

OAuth Flow Object

Configuration for the OAuth Implicit flow

password

OAuth Flow Object

Configuration for the OAuth Resource Owner Password flow

clientCredentials

OAuth Flow Object

Configuration for the OAuth Client Credentials flow. Previously called application in OpenAPI 2.0.

authorizationCode

OAuth Flow Object

Configuration for the OAuth Authorization Code flow. Previously called accessCode in OpenAPI 2.0.

This object MAY be extended with Specification Extensions.

OAuth Flow Object

Configuration details for a supported OAuth Flow

Fixed Fields

Field Name

Type

Applies To

Description

authorizationUrl

string

oauth2 ("implicit", "authorizationCode")

REQUIRED. The authorization URL to be used for this flow. This MUST be in the form of a URL.

tokenUrl

string

oauth2 ("password", "clientCredentials", "authorizationCode")

REQUIRED. The token URL to be used for this flow. This MUST be in the form of a URL.

refreshUrl

string

oauth2

The URL to be used for obtaining refresh tokens. This MUST be in the form of a URL.

scopes

Map[string, string]

oauth2

REQUIRED. The available scopes for the OAuth2 security scheme. A map between the scope name and a short description for it. The map MAY be empty.

This object MAY be extended with Specification Extensions.

OAuth Flow Object Examples

{  "type": "oauth2",  "flows": {    "implicit": {      "authorizationUrl": "https://example.com/api/oauth/dialog",      "scopes": {        "write:pets": "modify pets in your account",        "read:pets": "read your pets"      }    },    "authorizationCode": {      "authorizationUrl": "https://example.com/api/oauth/dialog",      "tokenUrl": "https://example.com/api/oauth/token",      "scopes": {        "write:pets": "modify pets in your account",        "read:pets": "read your pets"      }    }  }}

type: oauth2flows:   implicit:    authorizationUrl: https://example.com/api/oauth/dialog    scopes:      write:pets: modify pets in your account      read:pets: read your pets  authorizationCode:    authorizationUrl: https://example.com/api/oauth/dialog    tokenUrl: https://example.com/api/oauth/token    scopes:      write:pets: modify pets in your account      read:pets: read your pets

Security Requirement Object

Lists the required security schemes to execute this operation. The name used for each property MUST correspond to a security scheme declared in the Security Schemes under the Components Object.

Security Requirement Objects that contain multiple schemes require that all schemes MUST be satisfied for a request to be authorized. This enables support for scenarios where multiple query parameters or HTTP headers are required to convey security information.

When a list of Security Requirement Objects is defined on the OpenAPI Object or Operation Object, only one of the Security Requirement Objects in the list needs to be satisfied to authorize the request.

Patterned Fields

Field Pattern

Type

Description

{name}

[string]

Each name MUST correspond to a security scheme which is declared in the Security Schemes under the Components Object. If the security scheme is of type "oauth2" or "openIdConnect", then the value is a list of scope names required for the execution, and the list MAY be empty if authorization does not require a specified scope. For other security scheme types, the array MUST be empty.

Security Requirement Object Examples

Non-OAuth2 Security Requirement

{  "api_key": []}

api_key: []

OAuth2 Security Requirement

{  "petstore_auth": [    "write:pets",    "read:pets"  ]}

petstore_auth:- write:pets- read:pets

Optional OAuth2 Security

Optional OAuth2 security as would be defined in an OpenAPI Object or an Operation Object:

{  "security": [    {},    {      "petstore_auth": [        "write:pets",        "read:pets"      ]    }  ]}

security:  - {}  - petstore_auth:    - write:pets    - read:pets

Specification Extensions

While the OpenAPI Specification tries to accommodate most use cases, additional data can be added to extend the specification at certain points.

The extensions properties are implemented as patterned fields that are always prefixed by "x-".

Field Pattern

Type

Description

^x-

Any

Allows extensions to the OpenAPI Schema. The field name MUST begin with x-, for example, x-internal-id. The value can be null, a primitive, an array or an object. Can have any valid JSON format value.

The extensions may or may not be supported by the available tooling, but those may be extended as well to add requested support (if tools are internal or open-sourced).

Security Filtering

Some objects in the OpenAPI Specification MAY be declared and remain empty, or be completely removed, even though they are inherently the core of the API documentation.

The reasoning is to allow an additional layer of access control over the documentation. While not part of the specification itself, certain libraries MAY choose to allow access to parts of the documentation based on some form of authentication/authorization.

Two examples of this:

The Paths Object MAY be empty. It may be counterintuitive, but this may tell the viewer that they got to the right place, but can't access any documentation. They'd still have access to the Info Object which may contain additional information regarding authentication.
The Path Item Object MAY be empty. In this case, the viewer will be aware that the path exists, but will not be able to see any of its operations or parameters. This is different from hiding the path itself from the Paths Object, because the user will be aware of its existence. This allows the documentation provider to finely control what the viewer can see.

Appendix A: Revision History

Version

Date

Notes

3.0.3

2020-02-20

Patch release of the OpenAPI Specification 3.0.3

3.0.2

2018-10-08

Patch release of the OpenAPI Specification 3.0.2

3.0.1

2017-12-06

Patch release of the OpenAPI Specification 3.0.1

3.0.0

2017-07-26

Release of the OpenAPI Specification 3.0.0

3.0.0-rc2

2017-06-16

rc2 of the 3.0 specification

3.0.0-rc1

2017-04-27

rc1 of the 3.0 specification

3.0.0-rc0

2017-02-28

Implementer's Draft of the 3.0 specification

2.0

2015-12-31

Donation of Swagger 2.0 to the OpenAPI Initiative

2.0

2014-09-08

Release of Swagger 2.0

1.2

2014-03-14

Initial release of the formal document.

1.1

2012-08-22

Release of Swagger 1.1

1.0

2011-08-10

First release of the Swagger Specification

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