Toolchain Lens is a local MCP tool for explaining reproducibility signals in small projects. It looks at package-manager files, runtime declarations, container files, and CI configuration, then reports coarse contradictions and missing anchors.

Tool

explain_toolchain: inspect a local project without returning exact versions, dependency names, command output, environment values, or secret contents.

Safety

Local paths only, bounded by TOOLCHAIN_LENS_ROOT and realpath checks.
Reads only a bounded allowlist of toolchain and CI files.
Skips Git data, dependencies, build output, coverage, caches, and vendor directories.
Returns filenames, categories, and structural signal labels only.
This is an explanation aid, not a build executor, lockfile validator, or vulnerability scanner.

Run

npm install
npm run build
node dist/index.js

Quick start

npm install
npm run build
node dist/index.js

The server uses stdio, so it can be connected to Claude Desktop, Cursor, VS Code, MCP Inspector, or another compatible MCP client.

Tools at a glance

explain_toolchain: Explain local reproducibility signals and contradictions without returning exact versions, dependency names, or secret values.

Try it

After building, connect the server through your MCP client. The repository root also contains smoke-test.mjs for projects covered by the shared harness. A typical tool call starts with explain_toolchain.

Premium tools

These tools need a license key:

reproducibility_gap_matrix

Buy a key at https://mcp-marketplace.io/server/io-github-mrfentmen-toolchain-lens-mcp and set it in your MCP client config:

"env": { "MCP_LICENSE_KEY": "mcp_live_..." }

The key is checked against MCP Marketplace, cached for 24 hours, and keeps working offline once one check has succeeded. Every other tool on this server stays free.