Contract Diff compares two local JSON contract snapshots and reports a coarse structural fingerprint. It is useful for quickly answering whether a generated API or schema snapshot became larger, smaller, or structurally different without handing schema contents to an agent. It does not prove endpoint compatibility or identify semantic additions and removals.

Tool

compare_contract_snapshots: compare two local JSON snapshots using node counts, value type categories, and deltas only. The result is a structural signal, not a semantic contract diff.

Safety

Local paths only, bounded by CONTRACT_DIFF_ROOT and realpath checks.
Files are capped at two megabytes and traversal is capped.
Never returns schema names, paths, values, descriptions, examples, versions, file paths, or raw contents.
This is a coarse regression signal, not a complete OpenAPI or JSON Schema compatibility validator.

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

compare_contract_snapshots: Compare two local JSON contract snapshots using a coarse structural fingerprint; schema names, paths, values, and versions are never returned.

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 compare_contract_snapshots.

Premium tools

These tools need a license key:

contract_risk

Buy a key at https://mcp-marketplace.io/server/io-github-mrfentmen-contract-diff-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.