> ## Documentation Index > Fetch the complete documentation index at: https://docs.opper.ai/llms.txt > Use this file to discover all available pages before exploring further. # Chat Completions > OpenAI-compatible chat completions endpoint. Supports streaming via the stream parameter. ## OpenAPI ````yaml post /v3/compat/chat/completions openapi: 3.1.0 info: description: Schema-driven generative API that orchestrates LLM-powered workflows. title: Task API version: 3.0.0 servers: - description: Production url: https://api.opper.ai - description: Local development url: http://localhost:8080 security: - BearerAuth: [] tags: - description: Schema-driven function management and execution name: Functions - description: OpenAI-compatible chat completions name: Chat - description: OpenAI Responses API compatible endpoint name: Responses - description: Google-compatible interactions endpoint name: Interactions - description: Model registry and capabilities name: Models - description: Synchronous image generation name: Images - description: Text-to-speech and speech-to-text name: Audio - description: Asynchronous video generation name: Videos - description: Reusable file storage for media inputs and generated outputs name: Files - description: Async generation status and downloads name: Artifacts - description: OpenAI-compatible embeddings name: Embeddings - description: Recorded HTTP request/response generations name: Generations - description: System health and status name: System - description: Roundtable endpoint — fan out a query to multiple LLMs and combine results name: Roundtable - description: Web search, fetch, and other utility tools name: Tools paths: /v3/compat/chat/completions: post: tags: - Compatibility summary: Chat Completions API description: >- OpenAI-compatible chat completions endpoint. Supports streaming via the stream parameter. operationId: chatCompletions parameters: - description: >- Function name for tracing and project-level guardrail function-scope filtering. in: header name: X-Opper-Name schema: type: string - description: Parent span ID for distributed tracing context. in: header name: X-Opper-Parent-Span-Id schema: format: uuid type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/ChatRequest' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/ChatResponse' text/event-stream: schema: description: >- Server-Sent Events stream. Each event is `data: ` (a `chat.completion.chunk` object). The stream terminates with `data: [DONE]`. When `stream_options.include_usage` is true, the final chunk before `[DONE]` carries `usage` and an Opper `cost` extension. type: string description: Successful response headers: X-Opper-Cost: description: Execution cost of the request as a floating-point number. schema: format: double type: number '400': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Bad request '401': description: Unauthorized - missing or invalid API key '500': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Internal server error components: schemas: ChatRequest: properties: custom_model_credentials: properties: api_key: type: string base_url: type: string extra: type: object identifier: type: string url: type: string required: - identifier - api_key type: object max_completion_tokens: type: integer max_tokens: type: integer messages: items: properties: content: description: Any value name: type: string role: type: string tool_call_id: type: string tool_calls: items: properties: function: properties: arguments: type: string name: type: string required: - name - arguments type: object id: type: string thought_signature: type: string type: type: string required: - id - type - function type: object type: array required: - role - content type: object type: array model: type: string output_schema: type: object reasoning_effort: type: string response_format: type: object stop: items: type: string type: array stream: type: boolean stream_options: properties: include_usage: type: boolean type: object temperature: type: number tool_choice: description: Any value tools: items: properties: aspect_ratio: type: string function: properties: description: type: string name: type: string parameters: type: object required: - name type: object model: type: string quality: type: string size: type: string style: type: string type: type: string required: - type type: object type: array top_p: type: number required: - messages type: object ChatResponse: properties: choices: items: properties: finish_reason: type: string index: type: integer message: properties: annotations: items: properties: type: type: string url_citation: properties: content: type: string end_index: type: integer start_index: type: integer title: type: string url: type: string required: - url type: object required: - type type: object type: array content: type: string reasoning_content: type: string role: type: string tool_calls: items: properties: function: properties: arguments: type: string name: type: string required: - name - arguments type: object id: type: string thought_signature: type: string type: type: string required: - id - type - function type: object type: array required: - role - content type: object required: - index - message - finish_reason type: object type: array cost: type: number created: type: integer id: type: string meta: properties: guards: items: properties: code: type: string findings: items: description: Any value type: array flagged: type: boolean phase: type: string rule_id: type: string rule_name: type: string scope_type: type: string status: type: string type: type: string required: - type - flagged type: object type: array trace_uuid: type: string type: object model: type: string object: type: string usage: properties: completion_tokens: type: integer completion_tokens_details: properties: reasoning_tokens: type: integer required: - reasoning_tokens type: object prompt_tokens: type: integer prompt_tokens_details: properties: cache_creation_1h_tokens: type: integer cache_creation_tokens: type: integer cached_tokens: type: integer type: object server_tool_use: type: object total_tokens: type: integer required: - prompt_tokens - completion_tokens - total_tokens type: object required: - id - object - created - model - choices - usage type: object ErrorResponse: properties: error: properties: code: type: string details: description: Any value message: type: string required: - code - message type: object meta: type: object required: - error type: object securitySchemes: BearerAuth: bearerFormat: API Key description: API key authentication. Pass your API key as a Bearer token. scheme: bearer type: http ````