> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-5e9cc07a-preview-update-1770920925-e15dbde.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Call agents from code

> Invoke Agent Builder agents from Python or JavaScript using the LangGraph SDK.

You can invoke Agent Builder agents from your applications using the [LangGraph SDK](/langsmith/sdk). Agent Builder agents run on [Agent Server](/langsmith/agent-server), so you can use the same API methods as any other [LangSmith deployment](/langsmith/deployments).

## Prerequisites

* A LangSmith account with an Agent Builder agent
* A [Personal Access Token (PAT)](/langsmith/create-account-api-key) for authentication
* The [LangGraph SDK](/langsmith/sdk) installed:

<CodeGroup>
  ```bash Python theme={null}
  pip install langgraph-sdk python-dotenv
  ```

  ```bash TypeScript theme={null}
  yarn add @langchain/langgraph-sdk
  ```
</CodeGroup>

## Authentication

To authenticate with your agent's Agent Builder deployment, provide a LangSmith [Personal Access Token (PAT)](/langsmith/create-account-api-key) to the `api_key` argument when instantiating the LangGraph SDK client, or via the `X-API-Key` header. If using `X-API-Key`, you must also set the `X-Auth-Scheme` header to `langsmith-api-key`.

If the PAT you pass is not tied to the owner of the agent, your request will be rejected with a `404 Not Found` error.

If the agent you're trying to invoke is a <Tooltip tip="Agents shared with all members of a LangSmith workspace. Private agents are only visible to the creator." cta="Learn more" href="/langsmith/agent-builder-workspace-vs-private">workspace agent</Tooltip> and you're not the owner, you can perform all the same operations as you would in the UI (read-only).

## Example

To get your agent's `agent_id` and `api_url`:

1. Navigate to the agent in Agent Builder.
2. Click the <Icon icon="gear" /> settings icon in the top right corner.
3. Click **View code snippets** to see pre-populated values for your agent.

Copy the code below and replace `agent_id` and `api_url` with the values from your agent's code snippets.

Create a `.env` file in your project root with your [Personal Access Token](/langsmith/create-account-api-key):

```bash .env theme={null}
LANGGRAPH_API_KEY=your-personal-access-token
```

<Tabs>
  <Tab title="Python">
    ```python theme={null}
    import os
    from dotenv import load_dotenv
    from langgraph_sdk.client import get_client

    load_dotenv()

    agent_id = "your-agent-id"

    # This must be a PAT tied to your LangSmith account
    api_key = os.getenv("LANGGRAPH_API_KEY")
    api_url = "https://prod-agent-builder-5ccea139413e5ef289ab8e5d04688e11.us.langgraph.app"

    client = get_client(
        url=api_url,
        api_key=api_key,
        headers={
            "X-Auth-Scheme": "langsmith-api-key",
        },
    )

    async def get_assistant(agent_id: str):
        agent = await client.assistants.get(agent_id)
        print(agent)

    if __name__ == "__main__":
        import asyncio
        asyncio.run(get_assistant(agent_id))
    ```
  </Tab>

  <Tab title="TypeScript">
    ```ts theme={null}
    import "dotenv/config";
    import { Client } from "@langchain/langgraph-sdk";

    const agentId = "your-agent-id";

    // This must be a PAT tied to your LangSmith account
    const apiKey = process.env.LANGGRAPH_API_KEY;
    const apiUrl = "https://prod-agent-builder-5ccea139413e5ef289ab8e5d04688e11.us.langgraph.app";

    const client = new Client({
      apiUrl,
      apiKey,
      defaultHeaders: {
        "X-Auth-Scheme": "langsmith-api-key",
      },
    });

    async function main(agentId: string) {
      const agent = await client.assistants.get(agentId);
      console.log(agent);
    }

    main(agentId).catch(console.error);
    ```
  </Tab>
</Tabs>

<Callout icon="key" color="#FEF3C7" iconType="regular">
  Use a [Personal Access Token (PAT)](/langsmith/create-account-api-key) tied to your LangSmith account. Set the `X-Auth-Scheme` header to `langsmith-api-key` for authentication. If you implemented custom authentication, pass the user's token in headers so the agent can use user-scoped tools. See [Add custom authentication](/langsmith/custom-auth).
</Callout>

***

<Callout icon="pen-to-square" iconType="regular">
  [Edit this page on GitHub](https://github.com/langchain-ai/docs/edit/main/src/langsmith/agent-builder-code.mdx) or [file an issue](https://github.com/langchain-ai/docs/issues/new/choose).
</Callout>

<Tip icon="terminal" iconType="regular">
  [Connect these docs](/use-these-docs) to Claude, VSCode, and more via MCP for real-time answers.
</Tip>