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We tested 25 approaches to MCP tool search, including decision models, LLMs, and embeddings. Our benchmark runs 150 search queries against 536 tools. We settled on weighted BM25 with a few normalization rules. Fast, local, no model or API calls.

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For graphics tools, I'd test “round corners” against “fillet” too; users may never use the API's terminology.

BM25 with normalization beating an LLM over 536 tools is the most welcome result I have read all month. Tool search is a lookup problem wearing a hype hat, and the boring answer keeps winning. Fast, local, no API calls, no bill.

Love this result. The boring, fast, local option beating 24 fancier approaches is such a good reminder — not every search problem needs a model, sometimes it just needs good ranking.

Well. Generally, you just set temperature to zero, give the same input on the same hardware and receive the same output.

Curious, did BM25 beat the decision models on accuracy or mainly on latency and cost? Or did the models get close enough that a hybrid rerank was worth the extra pass?