Send Message Streaming

POST
/v1/agents/:agent_id/messages/stream

Process a user message and return the agent’s response. This endpoint accepts a message from a user and processes it through the agent. It will stream the steps of the response always, and stream the tokens if ‘stream_tokens’ is set to True.

Path parameters

agent_idstringRequired

Request

This endpoint expects an object.
messageslist of objectsRequired

The messages to be sent to the agent.

use_assistant_messagebooleanOptionalDefaults to true

Whether the server should parse specific tool call arguments (default send_message) as AssistantMessage objects.

assistant_message_tool_namestringOptionalDefaults to send_message

The name of the designated message tool.

assistant_message_tool_kwargstringOptionalDefaults to message

The name of the message argument in the designated message tool.

stream_tokensbooleanOptionalDefaults to false

Flag to determine if individual tokens should be streamed. Set to True for token streaming (requires stream_steps = True).

Response

Successful response

System Messageobject or null
OR
User Messageobject or null
OR
Reasoning Messageobject or null
OR
Tool Call Messageobject or null
OR
Tool Return Messageobject or null
OR
Assistant Messageobject or null
OR
Letta Usage Statisticsobject or null

Errors

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