How to trace your vibe-coded agent with W&B Weave
The video demonstrates how to implement comprehensive observability for AI agents using Weights & Biases (W&B) Weave and the W&B MCP server. By leveraging the `weave for agents SDK`, engineers can add full tracing—including conversations, turns, LLM calls, and tool executions—to an existing agent's logic without modifying its core code. This instrumentation allows developers to monitor performance metrics, track resource usage (tokens, cost), and debug complex interactions, such as identifying model hallucinations.
Key takeaways
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Weave provides deep observability for AI agents
The tracing structure follows a clear hierarchy: Agent $\to$ Conversation $\to$ Turn $\to$ LLM Call + Tool Call. This detailed view is crucial for understanding agent behavior and performance.
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Non-invasive instrumentation using W&B MCP
Observability can be added by prompting a coding assistant (like Claude Code) to inject the necessary tracing logic via the `weave for agents SDK`, avoiding changes to existing application code.
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Debugging and Evaluation Capabilities
The Weave UI allows engineers to inspect individual conversations and turns, providing step-by-step visibility into tool usage (e.g., Tavali search) and LLM decisions. This is critical for debugging hallucinations or unexpected agent behavior.