Anthropic Discover a Model and Send a Message

arazzo: 1.0.1
info:
  title: Anthropic Discover a Model and Send a Message
  summary: List available models, confirm a chosen model exists, then create a message with it.
  description: >-
    A model-discovery to generation flow against the Anthropic Models API. The
    workflow first lists the models available to the account, then resolves the
    requested model alias to confirm it is usable, and finally sends a single
    text message to that model and captures the generated content. Every step
    spells out its request inline — including the inline x-api-key and
    anthropic-version headers the spec defines — so the flow can be read and
    executed without opening the underlying OpenAPI description.
  version: 1.0.0
sourceDescriptions:
- name: messagesApi
  url: ../openapi/anthropic-messages-api-openapi.yml
  type: openapi
- name: modelsApi
  url: ../openapi/anthropic-models-api-openapi.yml
  type: openapi
workflows:
- workflowId: discover-model-and-message
  summary: Pick an available model, validate it, and generate a message with it.
  description: >-
    Lists the available Claude models, confirms the requested model id resolves
    via the Get Model endpoint, and then calls Create Message to generate a
    response from that model.
  inputs:
    type: object
    required:
    - apiKey
    - modelId
    - prompt
    properties:
      apiKey:
        type: string
        description: A valid Anthropic API key sent in the x-api-key header.
      modelId:
        type: string
        description: The model id or alias to validate and use (e.g. claude-sonnet-4-20250514).
      prompt:
        type: string
        description: The user prompt text to send to the model.
      maxTokens:
        type: integer
        description: Maximum number of tokens to generate.
        default: 1024
  steps:
  - stepId: listModels
    description: >-
      List the models available to this account so a caller can confirm the
      desired model is present before using it.
    operationId: models_list
    parameters:
    - name: x-api-key
      in: header
      value: $inputs.apiKey
    - name: anthropic-version
      in: header
      value: "2023-06-01"
    - name: limit
      in: query
      value: 20
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      firstModelId: $response.body#/data/0/id
      hasMore: $response.body#/has_more
  - stepId: validateModel
    description: >-
      Resolve the requested model id to confirm it exists and is available
      before attempting to generate a message with it.
    operationId: models_get
    parameters:
    - name: model_id
      in: path
      value: $inputs.modelId
    - name: x-api-key
      in: header
      value: $inputs.apiKey
    - name: anthropic-version
      in: header
      value: "2023-06-01"
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      resolvedModelId: $response.body#/id
      displayName: $response.body#/display_name
  - stepId: createMessage
    description: >-
      Send a single user message to the validated model and capture the
      generated content and token usage.
    operationId: messages_post
    parameters:
    - name: x-api-key
      in: header
      value: $inputs.apiKey
    - name: anthropic-version
      in: header
      value: "2023-06-01"
    - name: Content-Type
      in: header
      value: application/json
    requestBody:
      contentType: application/json
      payload:
        model: $steps.validateModel.outputs.resolvedModelId
        max_tokens: $inputs.maxTokens
        messages:
        - role: user
          content: $inputs.prompt
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      messageId: $response.body#/id
      content: $response.body#/content
      stopReason: $response.body#/stop_reason
      usage: $response.body#/usage
  outputs:
    resolvedModelId: $steps.validateModel.outputs.resolvedModelId
    messageId: $steps.createMessage.outputs.messageId
    content: $steps.createMessage.outputs.content
    usage: $steps.createMessage.outputs.usage