Vercel AI Gateway Cost-Routed Two-Turn Conversation

arazzo: 1.0.1
info:
  title: Vercel AI Gateway Cost-Routed Two-Turn Conversation
  summary: Run a cost-sorted chat completion, then send a follow-up turn carrying the prior reply.
  description: >-
    A two-turn conversation flow for the Vercel AI Gateway that routes by cost. The
    first step sends a chat completion with the gateway sort set to cost, and the
    second step continues the conversation by replaying the user prompt, the
    assistant reply captured from the first step, and a follow-up message so the
    model answers with full context. Each step inlines its request and documents
    the success status.
  version: 1.0.0
sourceDescriptions:
- name: chatApi
  url: ../openapi/vercel-chat-api-openapi.yml
  type: openapi
workflows:
- workflowId: costRoutedConversation
  summary: Two cost-routed chat completions chained into a single conversation.
  description: >-
    Issues a first cost-sorted chat completion, then sends a second completion that
    includes the first assistant reply and a follow-up message to continue the
    conversation.
  inputs:
    type: object
    required:
    - apiKey
    - model
    - prompt
    - followUp
    properties:
      apiKey:
        type: string
        description: Vercel AI Gateway API key (AI_GATEWAY_API_KEY) used as a Bearer token.
      model:
        type: string
        description: "Model id in 'provider/model-name' form."
      prompt:
        type: string
        description: The initial user message.
      followUp:
        type: string
        description: The follow-up user message for the second turn.
  steps:
  - stepId: firstTurn
    description: >-
      Send the first chat completion, sorting providers by cost via the gateway
      routing options.
    operationId: createChatCompletion
    parameters:
    - name: Authorization
      in: header
      value: Bearer $inputs.apiKey
    requestBody:
      contentType: application/json
      payload:
        model: $inputs.model
        messages:
        - role: user
          content: $inputs.prompt
        stream: false
        providerOptions:
          gateway:
            sort: cost
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      firstReply: $response.body#/choices/0/message/content
  - stepId: secondTurn
    description: >-
      Continue the conversation by replaying the prior user and assistant turns
      and appending the follow-up message, again sorting by cost.
    operationId: createChatCompletion
    parameters:
    - name: Authorization
      in: header
      value: Bearer $inputs.apiKey
    requestBody:
      contentType: application/json
      payload:
        model: $inputs.model
        messages:
        - role: user
          content: $inputs.prompt
        - role: assistant
          content: $steps.firstTurn.outputs.firstReply
        - role: user
          content: $inputs.followUp
        stream: false
        providerOptions:
          gateway:
            sort: cost
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      secondReply: $response.body#/choices/0/message/content
      finishReason: $response.body#/choices/0/finish_reason
      totalTokens: $response.body#/usage/total_tokens
  outputs:
    firstReply: $steps.firstTurn.outputs.firstReply
    secondReply: $steps.secondTurn.outputs.secondReply
    totalTokens: $steps.secondTurn.outputs.totalTokens