How to define different body parameters for same path in OpenAPI (Swagger)?

Question

I have a service that can have two different kind of body parameters based on the Content-Type header.

E.g. for path /Pet:

• If Content-Type: application/somecustom.resource+json is used, then POST can take up Pet as the body parameter.

• If Content-Type: application/somecustom.function+json is used, then POST should take up some different body parameter to invoke a function and return a different response.

Any suggestion on how to manifest this in OpenAPI (Swagger)?

Answer 1

OpenAPI 3.0 supports different schemas per media type.

openapi: 3.0.0
...
paths:
  /pet:
    post:
      requestBody:
        required: true
        content:
          application/somecustom.resource+json:
            schema:
              $ref: '#/components/schemas/Pet'
          application/somecustom.function+json:
            schema:
              $ref: '#/components/schemas/Foo'

Answer 2

No, it's not possible to define a two different body parameters for the same operation, in the same path item. The path item name are unique by virtue of being property names (and therefore "keys" in the JSON key-value map), and Swagger specification allows at most one body parameter in a given operation.

There are a few alternative approaches to address this need:

Create two separate path items

For example:

/pets/createFromDescription:
  post:
    summary: Create a pet from a basic description
    operationId: createPetFromDescription
    parameters:
      - name: petDescription
        in: body
        required: true
        schema:
          $ref: "#/definitions/PetDescriptionObject"
    responses:
      200:
        description: OK
/pets/createFromCatalog:
  post:
    summary: Create a pet from a standard catalog entry
    operationId: createPetFromCatalogEntry
    parameters:
      - name: petCatalogEntry
        in: body
        required: true
        schema:
          $ref: "#/definitions/PetCatalogEntry"
    responses:
      200:
        description: OK

Create subtypes, with a discriminator

Described in the Swagger–OpenAPI 2.0 specification here.

Example:

/pets:
  post:
    summary: Create a pet 
    operationId: createPet
    parameters:
      - name: petSource
        in: body
        description: Structured pet information, from which to create the object 
        required: true
        schema:
          $ref: "#/definitions/CreatePet_Request"
    responses:
      200:
        description: OK

definitions:
  CreatePet_Request:
    type: object
    properties:
      requestVariant:
        type: string
    required:
    - requestVariant
    discriminator: requestVariant

  PetDescriptionObject:
    allOf:
    - $ref: "#/definitions/CreatePet_Request"
    - type: object
      properties: 
        name: 
          type: string
        description:
          type: string

  PetCatalogEntry:
    allOf:
    - $ref: "#/definitions/CreatePet_Request"
    - type: object
      properties: 
        SKU: 
          type: string
        Breed:
          type: string
        Comments:
          type: string

Neither of these methods is keyed to the media type of the request. While your request may accept multiple media types, if the use of a particular media type implies some requirement about the request body, you'd have to document that in the description property of the operation or body parameter.