Building Custom Multi-Agent Tools

Tip

We recommend using the pre-made multi-agent messaging tools for most use cases, but advanced users can write custom tools to support complex communication patterns.

You can also write your own agent communication tools by using the Letta API and writing a custom tool in Python. Since Letta runs as a service, you can make request to the server from a custom tool to send messages to other agents via API calls.

Here’s a simple example of a tool that sends a message to a specific agent:

TypeScript

async function customSendMessageToAgent(
  targetAgentId: string,
  messageContents: string,
) {
  /**
   * Send a message to a specific Letta agent.
   *
   * @param targetAgentId - The identifier of the target Letta agent.
   * @param messageContents - The message to be sent to the target Letta agent.
   */
  const { LettaClient } = require("@letta-ai/letta-client");

  // TODO: point this to the server where the worker agents are running
  const client = new LettaClient({ baseUrl: "http://127.0.0.1:8283" });

  // message all worker agents async
  const response = await client.agents.sendMessageAsync(
    targetAgentId,
    messageContents,
  );
}

Python

def custom_send_message_to_agent(target_agent_id: str, message_contents: str):
    """
    Send a message to a specific Letta agent.

    Args:
        target_agent_id (str): The identifier of the target Letta agent.
        message_contents (str): The message to be sent to the target Letta agent.
    """
    from letta_client import Letta

    # TODO: point this to the server where the worker agents are running
    client = Letta(base_url="http://127.0.0.1:8283")

    # message all worker agents async
    response = client.agents.send_message_async(
        agent_id=target_agent_id,
        message=message_contents,
    )

Below is an example of a tool that triggers agents tagged with worker to start their tasks:

TypeScript

async function triggerWorkerAgents() {
  /**
   * Trigger worker agents to start their tasks, without waiting for a response.
   */
  const { LettaClient } = require("@letta-ai/letta-client");

  // TODO: point this to the server where the worker agents are running
  const client = new LettaClient({ baseUrl: "http://127.0.0.1:8283" });

  // message all worker agents async
  const agents = await client.agents.list({ tags: ["worker"] });
  for (const agent of agents) {
    const response = await client.agents.sendMessageAsync(
      agent.id,
      "Start my task",
    );
  }
}

Python

def trigger_worker_agents():
    """
    Trigger worker agents to start their tasks, without waiting for a response.
    """
    from letta_client import Letta

    # TODO: point this to the server where the worker agents are running
    client = Letta(base_url="http://127.0.0.1:8283")

    # message all worker agents async
    for agent in client.agents.list(tags=["worker"]):
        response = client.agents.send_message_async(
            agent_id=agent.id,
            message="Start my task",
        )