Letta Send Agent Message Example

{
  "operation": "Send Agent Message",
  "method": "POST",
  "path": "/v1/agents/{agent_id}/messages",
  "auth": "Bearer token (LETTA_API_KEY)",
  "request": {
    "method": "POST",
    "path": "/v1/agents/agent-2f6d4a13/messages",
    "headers": {
      "Authorization": "Bearer $LETTA_API_KEY",
      "Content-Type": "application/json"
    },
    "body": {
      "messages": [
        {
          "role": "user",
          "content": [
            {
              "type": "text",
              "text": "Hi, can you remember that I prefer concise answers?"
            }
          ]
        }
      ]
    }
  },
  "response": {
    "status": 200,
    "body": {
      "run_id": "run-77a3",
      "messages": [
        {
          "message_type": "reasoning_message",
          "reasoning": "Update core memory: human prefers concise answers."
        },
        {
          "message_type": "tool_call_message",
          "tool_call": {
            "name": "core_memory_append",
            "arguments": {
              "label": "human",
              "content": "Prefers concise answers."
            }
          }
        },
        {
          "message_type": "tool_return_message",
          "tool_return": "OK"
        },
        {
          "message_type": "assistant_message",
          "content": "Got it \u2014 I will keep answers concise."
        }
      ],
      "usage": {
        "completion_tokens": 86,
        "prompt_tokens": 1240,
        "total_tokens": 1326,
        "step_count": 1
      }
    }
  }
}