toolc

The optimizing compiler for agent tool surfaces. Point it at your MCP servers, or just a REST API's OpenAPI spec, or even a docs page, and get back one endpoint that serves a smaller, smarter tool surface: cheaper for every agent that connects, more accurate on every task, with every call logged.

Connecting N MCP servers dumps every tool definition into the model's context, degrades tool selection, and forces improvised multi-hop call chains. toolc compiles the federation instead:

• Rewrite: LLM-optimized descriptions with sibling disambiguation

• Consolidate: families of near-duplicate tools (search_x/find_x/get_x) merge into single facade tools with deterministic routing

• Selection: the whole catalog compresses behind two meta-tools (search_tools/call_tool) when you want maximum context savings

• Compaction: oversized results are summarized at serve time, preserving identifiers and sourcing details

• Compose: REST APIs join the pool straight from an OpenAPI spec, or from a drafted spec synthesized from their documentation

• Observe: every call logged with arguments and results; recurring errors cluster into recommended fixes

Benchmark

131 tools across 5 live servers, 30 tasks × 3 trials, judged answers (full grid · consolidation run):

Consolidation dominates both ends of the frontier: the selection surface is the cost lever, consolidation lifts accuracy everywhere. Every pass is a config toggle; pick the tradeoff per deployment.

Related MCP server: auxiliar-mcp

Quick start

git clone https://github.com/toolc-dev/toolc && cd toolc
pnpm install && pnpm -r test

# describe your federation
cp toolc.config.example.jsonc toolc.config.jsonc

# introspect it
node packages/cli/bin/toolc.mjs -c toolc.config.jsonc inspect

# compile (set ANTHROPIC_API_KEY for the rewrite/consolidate passes)
node packages/cli/bin/toolc.mjs -c toolc.config.jsonc compile

# serve the compiled surface over stdio (add to Claude as an MCP server)
node packages/cli/bin/toolc.mjs -c toolc.config.jsonc serve --mode compiled

A downstream can be an MCP server or a bare REST API:

{
  "downstream": [
    { "id": "gh", "transport": { "type": "http", "url": "https://api.githubcopilot.com/mcp/" } },
    { "id": "nws", "transport": { "type": "openapi", "spec": "https://api.weather.gov/openapi.json" } }
  ]
}

See SELF_HOSTING.md for Docker deployment.

Hosted

toolc.dev runs this same engine as a managed service: compiled HTTPS endpoints, a console with a playground and full-payload log explorer, docs-to-spec drafting, and error-driven fix recommendations.

Layout

• packages/core: IR (Capability Graph), frontends (MCP, OpenAPI, docs synthesis), passes, emit

• packages/gateway: runtime MCP server (mirror + compiled) with call logging and compaction

• packages/cli: the toolc command

• packages/harness: benchmark runner, grading, reports

• packages/shared: config schema, errors

License

The engine (everything in this repository) is Apache-2.0, forever: anyone can compile and serve their own tool surfaces locally with the exact same compilation quality as the hosted product.