Introduction

OpenAPI Specification

OpenAPI Specification 3.0

The following is the OpenAPI Specification 3.0 file recreated based on Anthropic’s Messages API.

openapi: '3.0.3'
info:
  title: Anthropic API
  version: '1.0.0'
  contact:
    name: 'Anthropic Support'
    email: '[e-mail]'
    url: 'support.anthropic.com'
  description: "A recreation of Anthropic's Messages API as a sample project."
  termsOfService: 'https://www.anthropic.com/legal/consumer-terms'
externalDocs:
  url: 'https://docs.anthropic.com/claude/reference/messages_post'
  description: Anthropic official API documentation.
tags:
  - name: Messages
    description: 'Model messages'
paths:
  /messages:
    post:
      tags:
      - Messages 
      summary: 'Create a Message.'
      description: 'Send a structured list of input messages with text and/or image content, and the model will generate the next message in the conversation. The Messages API can be used for for either single queries or stateless multi-turn conversations.'
      parameters: []
      operationId: ''
      responses:
        '200':
          description: Message object.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/MessagesResponse'
        4XX:
          description: User error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        5XX:
          description: System error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - model
                - messages
                - max_tokens
              properties:
                model:
                  type: string
                  description: The model that will complete your prompt.
                messages:
                  type: array
                  description: Input messages.
                  example: '[{"role": "user", "content": "Hello, Claude"}]'
                  items:
                    type: object
                    properties:
                      role:
                        type: string
                        default: "user"
                      content:
                        type: string
                system:
                  type: string
                  description: >-
                    A system prompt is a way of providing context and
                    instructions to Claude, such as specifying a particular goal
                    or role.
                max_tokens:
                  type: integer
                  description: The maximum number of tokens to generate before stopping.
                metadata:
                  type: object
                  description: An object describing metadata about the request.
                stop_sequences:
                  type: array
                  description: >-
                    Custom text sequences that will cause the model to stop
                    generating.
                  items:
                    type: string
                stream:
                  type: boolean
                  description: >-
                    Whether to incrementally stream the response using
                    server-sent events.
                temperature:
                  type: number
                  description: Amount of randomness injected into the response.
                top_p:
                  type: number
                  description: Use nucleus sampling.
                top_k:
                  type: integer
                  description: >-
                    Only sample from the top K options for each subsequent
                    token.
              xml:
                name: Messages
        description: >-
          Model settings and a structured list of input messages with text
          and/or image content. 
security:
  - api-key: []
servers:
  - url: 'https://api.anthropic.com/v1'
    description: ''
    variables: {}
components:
  links: {}
  callbacks: {}
  schemas:
    MessagesResponse:
      type: object
      required:
        - id
        - type
        - role
        - content
        - model
        - stop_reason
        - stop_sequence
        - usage
      properties:
        id:
          type: string
          description: Unique object identifier.
        type:
          type: string
          description: 'For Messages, this is always "message".'
          default: "message"
        role:
          type: string
          description: This will always be "assistant".
          default: "assistant"
        content:
          type: array
          description: >-
            An array of content blocks, each of which has a type. Currently,
            only type in responses is "text".
          example: '[{"type": "text", "text": "Hi, I''m Claude."}]'
          items:
            type: object
            properties:
              type:
                type: string
                default: text
              text:
                type: string
        model:
          type: string
          description: The model that handled the request.
        stop_reason:
          type: string
          description: >-
            The reason that the model stopped. In non-streaming mode this value
            is always non-null. In streaming mode, it is null in the
            message_start event and non-null otherwise.
          enum:
            - end_turn
            - max_tokens
            - stop_sequence
        stop_sequence:
          type: string
          description: >-
            This value will be a non-null string if one of your custom stop
            sequences was generated. Else null.
        usage:
          type: object
          description: Billing and rate-limit usage.
          required:
            - input_tokens
            - output_tokens
          properties:
            input_tokens:
              type: integer
              description: The number of input tokens which were used.
            output_tokens:
              type: integer
              description: The number of output tokens which were used.
    ErrorResponse:
      type: object
      required:
        - type
        - error
      properties:
        type:
          type: string
          default: error
        error:
          type: object
          properties:
            type:
              type: string
              example: not_found_error
              enum:
                - APIERROR
                - AUTHENTICATIONERROR
                - INVALIDREQUESTERROR
                - NOTFOUNDERROR
                - OVERLOADEDERROR
                - PERMISSIONERROR
                - RATELIMITERROR
            message:
              type: string
              example: The requested resource could not be found.
  securitySchemes:
    api-key:
      type: apiKey
      name: x-api-key
      in: header
      description: API key to authorize requests.

Minor corrections and optimizations coming soon.