openapi: 3.0.3
info:
  title: Langbase Agent API
  description: Representative OpenAPI description of the Langbase serverless AI developer platform. All endpoints are served from https://api.langbase.com and authenticated with a Bearer API key. Generative endpoints (Pipes run, Agent run) return Server-Sent Events (SSE) when `stream` is true. This document is a faithful representative model authored by API Evangelist and is not the provider's official specification.
  termsOfService: https://langbase.com/terms
  contact:
    name: Langbase Support
    url: https://langbase.com/support
  version: '1.0'
servers:
- url: https://api.langbase.com
  description: Langbase production API
security:
- api_key: []
tags:
- name: Agent
paths:
  /v1/agent/run:
    post:
      operationId: runAgent
      tags:
      - Agent
      summary: Run an agent against any of 100+ LLMs.
      description: Runs a prompt against a model specified as `provider:model_id` (for example `openai:gpt-4o-mini`). Supports tools, generation controls, and SSE streaming when `stream` is true. A bring-your-own LLM provider key may be supplied via the `LB-LLM-Key` header.
      parameters:
      - in: header
        name: LB-LLM-Key
        required: false
        schema:
          type: string
        description: Optional LLM provider API key for bring-your-own-key runs.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/RunAgentRequest'
      responses:
        '200':
          description: An agent run response, or an SSE stream when stream is true.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/RunResponse'
            text/event-stream:
              schema:
                type: string
                description: Server-Sent Events stream of completion chunks.
components:
  schemas:
    Message:
      type: object
      properties:
        role:
          type: string
          enum:
          - system
          - user
          - assistant
          - tool
        content:
          type: string
        name:
          type: string
      required:
      - role
    RunAgentRequest:
      type: object
      properties:
        model:
          type: string
          description: Model as provider:model_id, e.g. openai:gpt-4o-mini.
          example: openai:gpt-4o-mini
        input:
          oneOf:
          - type: string
          - type: array
            items:
              $ref: '#/components/schemas/Message'
        instructions:
          type: string
        stream:
          type: boolean
          default: false
        tools:
          type: array
          items:
            type: object
        temperature:
          type: number
        top_p:
          type: number
        max_tokens:
          type: integer
      required:
      - model
      - input
    Usage:
      type: object
      properties:
        prompt_tokens:
          type: integer
        completion_tokens:
          type: integer
        total_tokens:
          type: integer
    RunResponse:
      type: object
      properties:
        completion:
          type: string
          description: The generated text completion.
        raw:
          type: object
          description: The raw upstream provider response.
        usage:
          $ref: '#/components/schemas/Usage'
  securitySchemes:
    api_key:
      type: http
      scheme: bearer
      bearerFormat: apiKey