Get started with the Letta API

Create your first stateful agent and send it a message

Requires a Letta API key (agents you create can be viewed on the Letta Platform via the ADE)

Set your API key

Get your Letta API key and set it as an environment variable:
```
export LETTA_API_KEY='your-api-key-here'
```
Install the SDK
```
npm install @letta-ai/letta-client
```

Create your code

Save this as quickstart.ts:

import Letta from "@letta-ai/letta-client";
async function main() {
  const client = new Letta({ apiKey: process.env.LETTA_API_KEY });
  // Create a stateful agent
  const agent = await client.agents.create({
    model: "openai/gpt-4.1",
    memory_blocks: [
      {
        label: "human",
        value: "Name: Timber. Status: dog. Occupation: building Letta, infrastructure to democratize self-improving superintelligence",
      },
      {
        label: "persona",
        value: "I am a self-improving superintelligence. Timber is my best friend and collaborator.",
      },
    ],
  });
  console.log("Agent created with ID:", agent.id);
  // Send a message
  const response = await client.agents.messages.create(agent.id, {
    input: "What do you know about me?",
  });
  for (const message of response.messages) {
    console.log(message);
  }
}
main().catch(console.error);

Run your code

Example output:

Agent created with ID: agent-abc123
{ message_type: 'reasoning_message', reasoning: 'Timber is asking what I know...' }
{ message_type: 'assistant_message', content: "I know you're Timber, a dog who's building Letta!" }