Send Message — Letta

Process a user message and return the agent’s response. This endpoint accepts a message from a user and processes it through the agent.

agent_idstringRequired

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.

Successful Response

messageslist of objects

The messages returned by the agent.

usageobject

The usage statistics of the agent.

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

1	{
2	"messages": [
3	{
4	"message_type": "assistant_message",
5	"assistant_message": "messages",
6	"date": "2024-01-15T09:30:00Z",
7	"id": "messages"
8	}
9	],
10	"usage": {
11	"completion_tokens": 1,
12	"prompt_tokens": 1,
13	"total_tokens": 1,
14	"step_count": 1
15	}
16	}