retrieval-lens
A black-box flight recorder for RAG retrieval inside MCP agents.
retrieval-lens is an MCP server that logs every retrieval step your RAG agent makes — what chunks were retrieved, their scores, sources, and rankings — so you can audit, replay, and diff retrieval runs after the fact.
The Problem
When a RAG agent gives a wrong answer, you need to know: did retrieval fail, or did generation fail? Right now there's no easy way to answer that. Your observability tool shows you the LLM call. It doesn't show you which chunks the model saw before it answered, what scores they had, or how retrieval changed between yesterday and today.
retrieval-lens fixes that. Every retrieval run is logged. Nothing is hidden.
Demo
When your RAG agent gives a wrong answer, ask retrieval-lens what it saw:
await mcp.call("retrieval_diff", {
run_id_a: "support-bot-before-embedding-refresh",
run_id_b: "support-bot-after-embedding-refresh",
match_by: "source"
});
