openapi: 3.1.0
info:
  title: Fast ACCOUNT_COSTS Chat API
  version: 0.1.0
tags:
- name: Chat
paths:
  /agents/v1/chat/completions:
    post:
      tags:
      - Chat
      summary: Create Chat Completion
      description: 'Create a chat completion (OpenAI-compatible).


        Uses litellm with provider fallback: Azure GPT-5.5 → Anthropic Sonnet 4.6.

        The model in the request is ignored — provider selection is automatic.'
      operationId: create_chat_completion_agents_v1_chat_completions_post
      security:
      - HTTPBearer: []
      - HTTPBearer: []
      parameters:
      - name: x-session-id
        in: header
        required: false
        schema:
          anyOf:
          - type: string
            maxLength: 255
          - type: 'null'
          description: Optional opaque conversation identifier. When provided, the call's Langfuse trace is grouped under this session_id, letting a multi-turn agentic conversation appear as one timeline. Clients should pass the same value across every turn of a single conversation.
          title: X-Session-Id
        description: Optional opaque conversation identifier. When provided, the call's Langfuse trace is grouped under this session_id, letting a multi-turn agentic conversation appear as one timeline. Clients should pass the same value across every turn of a single conversation.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ChatRequest'
      responses:
        '200':
          description: Successful Response
          content:
            application/json:
              schema: {}
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
components:
  schemas:
    ResponseFunction:
      properties:
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        arguments:
          type: string
          title: Arguments
      type: object
      required:
      - arguments
      title: ResponseFunction
    Function:
      properties:
        name:
          type: string
          title: Name
        description:
          anyOf:
          - type: string
          - type: 'null'
          title: Description
        parameters:
          title: Parameters
      type: object
      required:
      - name
      - parameters
      title: Function
    SystemMessage:
      properties:
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        role:
          type: string
          const: system
          title: Role
          default: system
        content:
          anyOf:
          - type: string
          - items:
              $ref: '#/components/schemas/TextContent'
            type: array
          title: Content
      type: object
      required:
      - content
      title: SystemMessage
    StreamOptions:
      properties:
        include_usage:
          type: boolean
          title: Include Usage
          default: true
      type: object
      title: StreamOptions
    ToolCall:
      properties:
        index:
          anyOf:
          - type: integer
          - type: 'null'
          title: Index
        id:
          anyOf:
          - type: string
          - type: 'null'
          title: Id
        type:
          type: string
          const: function
          title: Type
          default: function
        function:
          $ref: '#/components/schemas/ResponseFunction'
      type: object
      required:
      - function
      title: ToolCall
    UserMessage:
      properties:
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        role:
          type: string
          const: user
          title: Role
          default: user
        content:
          anyOf:
          - type: string
          - items:
              anyOf:
              - $ref: '#/components/schemas/TextContent'
              - $ref: '#/components/schemas/ImageContent'
            type: array
          title: Content
      type: object
      required:
      - content
      title: UserMessage
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
            - type: string
            - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
      type: object
      required:
      - loc
      - msg
      - type
      title: ValidationError
    ImageContent:
      properties:
        type:
          type: string
          const: image_url
          title: Type
          default: image
        image_url:
          $ref: '#/components/schemas/ImageUrl'
        cache_control:
          anyOf:
          - additionalProperties: true
            type: object
          - type: 'null'
          title: Cache Control
      type: object
      required:
      - image_url
      title: ImageContent
    Tool:
      properties:
        type:
          type: string
          const: function
          title: Type
          default: function
        function:
          $ref: '#/components/schemas/Function'
      type: object
      required:
      - function
      title: Tool
    ImageUrl:
      properties:
        url:
          type: string
          title: Url
        detail:
          anyOf:
          - type: string
          - type: 'null'
          title: Detail
          default: auto
      type: object
      required:
      - url
      title: ImageUrl
    ToolMessage:
      properties:
        role:
          type: string
          const: tool
          title: Role
          default: tool
        content:
          anyOf:
          - type: string
          - items:
              $ref: '#/components/schemas/ToolContent'
            type: array
          - items:
              additionalProperties: true
              type: object
            type: array
          title: Content
        tool_call_id:
          type: string
          title: Tool Call Id
      type: object
      required:
      - content
      - tool_call_id
      title: ToolMessage
    ToolContent:
      properties:
        type:
          type: string
          const: text
          title: Type
          default: text
        text:
          type: string
          title: Text
      type: object
      required:
      - text
      title: ToolContent
    ChatRequest:
      properties:
        messages:
          items:
            anyOf:
            - $ref: '#/components/schemas/SystemMessage'
            - $ref: '#/components/schemas/UserMessage'
            - $ref: '#/components/schemas/AssistantMessage'
            - $ref: '#/components/schemas/ToolMessage'
          type: array
          title: Messages
        model:
          type: string
          title: Model
          default: custom
        frequency_penalty:
          anyOf:
          - type: number
            maximum: 2.0
            minimum: -2.0
          - type: 'null'
          title: Frequency Penalty
          default: 0.0
        presence_penalty:
          anyOf:
          - type: number
            maximum: 2.0
            minimum: -2.0
          - type: 'null'
          title: Presence Penalty
          default: 0.0
        stream:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Stream
          default: false
        stream_options:
          anyOf:
          - $ref: '#/components/schemas/StreamOptions'
          - type: 'null'
        temperature:
          anyOf:
          - type: number
            maximum: 2.0
            minimum: 0.0
          - type: 'null'
          title: Temperature
          default: 1.0
        top_p:
          anyOf:
          - type: number
            maximum: 1.0
            minimum: 0.0
          - type: 'null'
          title: Top P
          default: 1.0
        user:
          anyOf:
          - type: string
          - type: 'null'
          title: User
        max_tokens:
          anyOf:
          - type: integer
          - type: 'null'
          title: Max Tokens
          default: 2048
        max_completion_tokens:
          anyOf:
          - type: integer
          - type: 'null'
          title: Max Completion Tokens
        reasoning_effort:
          anyOf:
          - type: string
            enum:
            - low
            - medium
            - high
          - type: 'null'
          title: Reasoning Effort
        n:
          anyOf:
          - type: integer
          - type: 'null'
          title: N
          default: 1
        tools:
          anyOf:
          - items:
              $ref: '#/components/schemas/Tool'
            type: array
          - type: 'null'
          title: Tools
        tool_choice:
          anyOf:
          - type: string
          - {}
          title: Tool Choice
          default: auto
        stop:
          anyOf:
          - items:
              type: string
            type: array
          - type: string
          - type: 'null'
          title: Stop
        extra_body:
          anyOf:
          - additionalProperties: true
            type: object
          - type: 'null'
          title: Extra Body
      type: object
      required:
      - messages
      title: ChatRequest
    AssistantMessage:
      properties:
        name:
          anyOf:
          - type: string
          - type: 'null'
          title: Name
        role:
          type: string
          const: assistant
          title: Role
          default: assistant
        content:
          anyOf:
          - type: string
          - items:
              anyOf:
              - $ref: '#/components/schemas/TextContent'
              - $ref: '#/components/schemas/ImageContent'
            type: array
          - type: 'null'
          title: Content
        tool_calls:
          anyOf:
          - items:
              $ref: '#/components/schemas/ToolCall'
            type: array
          - type: 'null'
          title: Tool Calls
      type: object
      title: AssistantMessage
    TextContent:
      properties:
        type:
          type: string
          const: text
          title: Type
          default: text
        text:
          type: string
          title: Text
        cache_control:
          anyOf:
          - additionalProperties: true
            type: object
          - type: 'null'
          title: Cache Control
      type: object
      required:
      - text
      title: TextContent
  securitySchemes:
    HTTPBearer:
      type: http
      scheme: bearer