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toolsift

A local MCP proxy that ends tool-definition bloat. toolsift sits between your agent and N upstream MCP servers and exposes a tiny surface — search_tools + invoke_tool — so the agent retrieves only the tools it needs for this turn instead of paying for 50+ JSON schemas up front.

When an agent is wired to several MCP servers, their tool definitions can eat a huge slice of the context window before the first message — schemas, descriptions, and parameter lists for dozens of tools the agent won’t use this turn. toolsift connects to your upstreams as a client, aggregates their tools into a local index, and re-exposes just two meta-tools. The agent calls search_tools("open a github issue") to pull back the handful of relevant definitions, then invoke_tool(...) to run one. This is the RAG-MCP / lazy-tool-loading pattern.

Terminal window
  toolsift


  tools: 28 · queries: 28 · k: 5 · baseline surface: 1342 tokens


  retriever   recall@5  mrr   tokens  saved
  ----------  --------  ----  ------  -----
  all-tools   1.00      1.00  1342    0%
  bm25        0.89      0.67  223     83%
  embeddings  1.00      0.90  242     82%
  hybrid      0.96      0.80  236     82%


  → embeddings: recall@5 1.00 · 82% fewer tokens than loading every tool

100% local

BM25 + optional local embeddings. No API key, no network beyond your own upstreams, no telemetry. Tool definitions never leave the machine.

Model-agnostic

Speaks MCP over stdio — works with Claude Code, Cursor, Codex, or any MCP client. No agent-specific plugins needed.

Three retrievers

BM25 (zero-dependency default), semantic embeddings via a 23 MB local model (no API key), and a hybrid RRF fusion of both. Pluggable EmbedFn for your own backend.

Key-free eval harness

Ships a deterministic eval that scores recall@k, MRR, and token savings against your own toolset — no API key needed. See benchmarks.

Install in one command

Section titled “Install in one command”
Terminal window
npx toolsift install

This wires toolsift into Claude Code and Cursor automatically. Restart your agent and it sees search_tools + invoke_tool instead of all N upstream definitions.

Next steps

Section titled “Next steps”
Quick start Write toolsift.json and wire it into your agent in two minutes.
MCP tools The agent-facing tools: search_tools, invoke_tool, list_servers, and pinned pass-throughs.
Benchmarks Recall@k, MRR, and token savings across six domains and 60 tools — measured, reproducible, honest.

MIT   MCP proxy   github.com/abdulmunimjemal/toolsift