> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wandb.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# W&B Weave

> Track, test, and improve language model apps with W&B Weave

W\&B Weave is an observability and evaluation platform that helps you track, evaluate, and improve your agents and LLM applications. With Weave, you can:

* [Trace and collect metrics about your agent built with popular SDKs and harnesses](/weave/agent-integration-quickstart)
* [Manually instrument custom-built agents to collect traces and metrics](/weave/custom-agents-quickstart)
* [Evaluate](/weave/tutorial-eval) your application’s responses using LLM judges and custom scorers

## Get started

The following docs guide you through the basics of how to use Weave's suite of tools.

<CardGroup cols={3}>
  <Card title="Integrate Weave with an agent" icon="plug" href="/weave/agent-integration-quickstart">
    Pick a built-in integration for your agent SDK or harness and start tracing sessions, turns, LLM calls, and tool calls in the Agents view.
  </Card>

  <Card title="Set up custom agent observability" icon="code" href="/weave/custom-agents-quickstart">
    Trace a custom multi-turn agent with the Weave SDK to capture sessions, LLM calls, and tool calls as OpenTelemetry spans.
  </Card>

  <Card title="View agent metrics in Weave UI" icon="chart-line" href="/weave/guides/tracking/view-agent-activity">
    Trace a basic call to an LLM and review the inputs, outputs, and code in your W\&B account.
  </Card>
</CardGroup>

## Install Weave

W\&B Weave provides Python and TypeScript libraries. To install the Weave library, run the following command:

<Tabs>
  <Tab title="Python">
    ```bash theme={null}
    pip install weave
    ```
  </Tab>

  <Tab title="TypeScript">
    ```bash theme={null}
    pnpm install weave
    ```
  </Tab>
</Tabs>

To start using the Weave library, create a [Weights & Biases (W\&B) account](https://wandb.ai) and an [API key at User Settings](https://wandb.ai/settings). The API key allows you to authenticate to your W\&B account and start sending data to it.