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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:

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Get started

Select your workload type and then use the following docs to guide you through the basics of how to use Weave’s suite of tools. For more information about the difference between workloads, see What is Weave?

Integrate Weave with an agent

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.

Set up custom agent observability

Trace a custom multi-turn agent with the Weave SDK to capture sessions, LLM calls, and tool calls as OpenTelemetry spans.

View agent metrics in Weave UI

Trace a basic call to an LLM and review the inputs, outputs, and code in your W&B account.

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Automatically instrument agents with Weave

To automatically instrument your agents to use Weave, update the following prompt with your project name and W&B API key environment variables, then pass the prompt to your agent:
Your agent installs Weave’s auto-instrumentation skill and uses it to:
  1. Install the Weave package, authenticate with W&B, and add weave.init("YOUR-TEAM-NAME/WEAVE_PROJECT") to agent entry points.
  2. Identify the codebase’s language, LLM/agent libraries, agent’s structure (loop, model calls, tool dispatch, sub-agents), and any existing OTel setup.
  3. Help you structure your trace data and properly instrument your application.
  4. Verify the configuration works by sending traces to your Weave project.
Once you’ve completed the configuration, your agents automatically start sending traces to Weave. If you want to manually instrument an agent, see Quickstart: Set up custom agent observability.