Send Message Streaming

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

Headers

AuthorizationstringRequired

Header authentication of the form Bearer <token>

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

User Messageobject

Reasoning Messageobject

Tool Call Messageobject

Tool Return Messageobject

Assistant Messageobject

Letta Usage Statisticsobject

1	curl -X POST https://api.letta.com/v1/agents/agent_id/messages/stream \
2	-H "Authorization: Bearer <token>" \
3	-H "Content-Type: application/json" \
4	-d '{
5	"messages": [
6	{
7	"role": "user",
8	"content": [
9	{
10	"type": "text",
11	"text": "text"
12	}
13	]
14	}
15	]
16	}'

Path parameters

Headers

Request

Response

Errors