Send Message

Send a message to the agent and stream the response.

This endpoint streams Server-Sent Events (SSE) back to the client as the agent processes the message through its workflow.

SSE Event Types

Core Events:

• intent: Intent classification result (emitted first)
  • {intent, confidence, category, reasoning, context_scope}
• thinking: Agent is analyzing/planning
  • {step, message}
• tool_call: Agent is calling a tool
  • {tool_name, tool_call_id, inputs}
• tool_result: Tool execution completed
  • {tool_name, tool_call_id, success, output, latency_ms}
• token: Response token (streaming)
  • {content}
• message: Final response content
  • {content, message_id, is_final}
• session_name: Auto-generated session name (first message only)
  • {session_name}
• done: Processing complete
  • {latency_ms, tool_calls_made, message_id, retriever_summary, data_accessed_via_retriever}
• error: Error occurred
  • {message, recoverable}

Retriever Events (IMPORTANT - Primary Data Pathway):

• retriever_execution: Retriever was used for data access
  • {tool_name, execution_id, retriever_id, is_adhoc, documents_returned, latency_ms, message}
  • Emitted whenever data is accessed via retriever (saved or ad-hoc)
• pipeline_config: Ad-hoc retriever configuration
  • {tool_name, config, message}
  • Contains the exact pipeline config users can save as a named retriever

Retriever Summary in done Event:

{
  "retriever_summary": {
    "used_retrievers": true,
    "retriever_count": 2,
    "saved_retrievers": 1,
    "adhoc_retrievers": 1,
    "total_documents": 25,
    "executions": [...]
  },
  "data_accessed_via_retriever": true
}

Args: request: FastAPI request with tenant context session_id: Session identifier payload: Message request

Returns: StreamingResponse with SSE events

Raises: NotFoundError: If session not found

Example:

curl -N -X POST http://localhost:8000/v1/agents/sessions/ses_abc123/messages \
  -H "Authorization: Bearer {api_key}" \
  -H "X-Namespace: {namespace_id}" \
  -H "Content-Type: application/json" \
  -d '{
    "content": "Find videos about machine learning",
    "stream": true
  }'

# SSE Output:
event: intent
data: {"intent": "retriever_search", "confidence": 0.92, "category": "retriever"}

event: thinking
data: {"step": "processing", "message": "Analyzing your request..."}

event: tool_call
data: {"tool_name": "execute_retriever", "tool_call_id": "run_abc", "inputs": {...}}

event: tool_result
data: {"tool_name": "execute_retriever", "success": true, "output": {...}}

event: retriever_execution
data: {"tool_name": "execute_retriever", "is_adhoc": false, "documents_returned": 5}

event: message
data: {"content": "I found 5 videos about machine learning...", "is_final": true}

event: done
data: {"latency_ms": 1250.5, "data_accessed_via_retriever": true, "retriever_summary": {...}}

POST /v1/agents/sessions/{session_id}/messages

Send Message

cURL

curl --request POST \
  --url https://api.mixpeek.com/v1/agents/sessions/{session_id}/messages \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-Namespace: <api-key>' \
  --data '
{
  "content": "<string>",
  "metadata": {},
  "stream": true
}
'

400

{
  "status": 123,
  "error": {
    "message": "<string>",
    "type": "<string>",
    "code": "<string>",
    "details": {}
  },
  "success": false
}

Authorizations

Authorization · string · header · required

Mixpeek API key, sent as Authorization: Bearer mxp_sk_.... Create one in Studio under Settings → API Keys, or with an admin key via POST /v1/organizations/users/{user_email}/api-keys. A missing header returns 403; an invalid or revoked key returns 401.

X-Namespace · string · header · required

Namespace id (ns_...), not the namespace name. This scopes the request rather than authenticating it, and it is required on every operation marked x-mixpeek-namespace-scoped.

Path Parameters

session_id · string · required

Session ID

Body

application/json

Request payload for sending a message to the agent.

Attributes: content: Message text content metadata: Optional message metadata stream: Whether to stream response as SSE (default: True)

Note: When stream=True, the response will be Server-Sent Events (SSE). When stream=False, the response will be a MessageResponse object.

Example: ```python # Streaming request (SSE) request = SendMessageRequest( content="Find videos about machine learning", stream=True )

# Non-streaming request
request = SendMessageRequest(
    content="Find videos about machine learning",
    stream=False
)
```

content · string · required

Message text content (REQUIRED)

Minimum string length: 1

metadata · Metadata · object

Message metadata (OPTIONAL)

stream · boolean · default: true

Stream response as SSE (default: True)

Response

200

application/json

Successful Response