> ## Documentation Index > Fetch the complete documentation index at: https://docs.routemcp.io/llms.txt > Use this file to discover all available pages before exploring further. # Stream a Chat Completion (SSE) > For clients that don't speak MCP JSON-RPC. Appends one user message to the `(workspace x x-session-id)` conversation, runs the agent loop, and streams the response as a `text/event-stream`. Reuse the same `x-session-id` across calls to continue the same conversation — the server persists message history per session. **Stateless workspaces:** if the workspace has `statelessMode: true`, nothing is persisted and the `x-session-id` header is ignored. Instead, supply prior turns yourself via the request body's `history` array (up to 200 turns; the current message stays in `message`). Sending `history` to a non-stateless workspace returns 400. `statelessMode` is a workspace setting and cannot be overridden per request. **SSE event types:** `message_delta` (incremental assistant text), `tool_call_start`, `tool_call_result`, `tool_calls_complete`, `usage` (token counts), `done` (stream end), and `error`. ## OpenAPI ````yaml POST /mcp/{workspaceId}/chat openapi: 3.0.0 info: title: RouteMCP API description: >- Unified API for integrations. Connect to multiple providers through a single API. version: '1.0' contact: {} servers: - url: https://api.routemcp.io/api/v1 description: Production security: - bearerAuth: [] tags: [] paths: /mcp/{workspaceId}/chat: post: tags: - HTTP Streaming Chat summary: Stream a chat completion (Server-Sent Events) description: >- For clients that don't speak MCP JSON-RPC. Appends one user message to the `(workspace x x-session-id)` conversation, runs the agent loop, and streams the response as a `text/event-stream`. Reuse the same `x-session-id` across calls to continue the same conversation — the server persists message history per session. **Stateless workspaces:** if the workspace has `statelessMode: true`, nothing is persisted and the `x-session-id` header is ignored. Instead, supply prior turns yourself via the request body's `history` array (up to 200 turns; the current message stays in `message`). Sending `history` to a non-stateless workspace returns 400. `statelessMode` is a workspace setting and cannot be overridden per request. **SSE event types:** `message_delta` (incremental assistant text), `tool_call_start`, `tool_call_result`, `tool_calls_complete`, `usage` (token counts), `done` (stream end), and `error`. operationId: McpChatController_sendMessage parameters: - name: workspaceId in: path required: true description: Workspace (MCP server) UUID to route the chat through. schema: type: string format: uuid - name: x-session-id in: header required: true description: >- Conversation id — must be a valid UUID. The same value across requests resumes the same chat; a new value starts a fresh conversation. schema: type: string format: uuid requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SendChatMessageDto' example: message: Hello responses: '200': description: >- Server-Sent Events stream of the agent loop's response. Parse `event:`/`data:` frames; the stream ends with a `done` event. content: text/event-stream: schema: type: string description: >- An SSE stream. Each frame is `event: \ndata: \n\n`. example: |+ event: message_delta data: {"text":"Hi"} event: tool_call_start data: {"id":"call_1","name":"github_list_repos"} event: tool_call_result data: {"id":"call_1","result":{...}} event: tool_calls_complete data: {} event: message_delta data: {"text":" there!"} event: usage data: {"inputTokens":1234,"outputTokens":56} event: done data: {} '400': description: Bad Request content: application/json: schema: type: object properties: success: type: boolean enum: - false example: false statusCode: type: integer example: 400 default: 400 message: type: string example: x-session-id must be a valid UUID default: Bad Request timestamp: type: string format: date-time example: '2026-02-06T12:00:00.000Z' path: type: string example: /api/v1/example required: - success - statusCode - message - timestamp - path '401': description: Unauthorized content: application/json: schema: type: object properties: success: type: boolean enum: - false example: false statusCode: type: integer example: 401 default: 401 message: type: string example: Invalid or missing API key default: Unauthorized timestamp: type: string format: date-time example: '2026-02-06T12:00:00.000Z' path: type: string example: /api/v1/example required: - success - statusCode - message - timestamp - path '404': description: Not Found content: application/json: schema: type: object properties: success: type: boolean enum: - false example: false statusCode: type: integer example: 404 default: 404 message: type: string example: mcp server not found default: Not Found timestamp: type: string format: date-time example: '2026-02-06T12:00:00.000Z' path: type: string example: /api/v1/example required: - success - statusCode - message - timestamp - path '429': description: Rate limit exceeded. content: application/json: schema: type: object properties: success: type: boolean enum: - false example: false statusCode: type: integer example: 429 default: 429 message: type: string example: Too Many Requests default: Too Many Requests timestamp: type: string format: date-time example: '2026-02-06T12:00:00.000Z' path: type: string example: /api/v1/example required: - success - statusCode - message - timestamp - path '500': description: Internal server error content: application/json: schema: type: object properties: success: type: boolean enum: - false example: false statusCode: type: integer example: 500 default: 500 message: type: string example: Internal server error. default: Internal server error. timestamp: type: string format: date-time example: '2026-02-06T12:00:00.000Z' path: type: string example: /api/v1/example required: - success - statusCode - message - timestamp - path security: - bearerAuth: [] components: schemas: SendChatMessageDto: type: object properties: message: type: string minLength: 1 maxLength: 50000 description: >- The user message for this turn. This is the CURRENT message only — prior turns go in `history` (stateless workspaces) or are loaded from the persisted session (stateful workspaces). example: Hello context: type: string maxLength: 50000 description: >- Optional free-text background about the end-user (e.g. an email signature, preferred tone, defaults). When non-empty it is injected into the agent so it can apply it when calling tools. On a stateful workspace it is stored encrypted and sticky for the end-user (keyed by the x-session-id header); on a stateless workspace it is injected for this request only and NEVER stored. Omit or send an empty string to keep any previously stored value; a new non-empty value overwrites it. Max 50000 characters. history: type: array maxItems: 200 description: >- Caller-supplied PRIOR conversation turns, accepted ONLY when the workspace is in `statelessMode`. Sending `history` to a non-stateless workspace returns 400. Excludes the current message (which stays in `message`). Up to 200 items; each item's `message` is capped at ~50,000 characters. items: type: object properties: role: type: string enum: - user - assistant example: user message: type: string minLength: 1 maxLength: 50000 example: What repos do I have? required: - role - message example: - role: user message: What repos do I have? - role: assistant message: 'You have 3 repositories: api, web, and docs.' required: - message securitySchemes: bearerAuth: type: apiKey in: header name: Authorization description: >- Enter your API key with the Bearer prefix — e.g. Bearer sk_live_xxx (production) or Bearer sk_test_xxx (sandbox) ````