Covenant
About
Contract & breaking-change detector for MCP servers — semver for your interface. Snapshot tools/resources/prompts into a lockfile, diff in CI, fail on breaking changes. Single Rust binary, SARIF, GitHub Action.
Details
- License
- MIT
Explore
- uses: actions/checkout@v4
- uses: dtolnay/rust-toolchain@stable
- uses: studiomeyer-io/[email protected]
cargo install mcp-covenant
Or build from source:
git clone https://github.com/studiomeyer-io/mcp-covenant
cd mcp-covenant && cargo build --release
mcp-covenant snapshot -o mcp-covenant.lock --http https://my-server.example/mcp
2. Check in CI — non-zero exit on a breaking change:
mcp-covenant check --fail-on breaking -- node dist/server.js
3. Lint the interface for schema hygiene (the things that quietly hurt tool selection):
$ mcp-covenant lint -- node dist/server.js
mcp-covenant lint: 2 finding(s) (0 error, 1 warning, 1 info)
WARNING (1)
tool:newtool — tool has no description; the model cannot tell when to call it [tool.missing_description]
INFO (1)
tool:search → limit — parameter has no description [tool.param.missing_description]
Everything also runs fully offline against two lockfiles — no server needed:
mcp-covenant check --baseline v1.lock --against v2.lock
mcp-covenant lint --from v1.lock
---
mcp-covenant
Contract & breaking-change detection for Model Context Protocol servers — semver for your MCP interface.
When you ship a typed library you have a public API and tooling that screams when you break
it. MCP servers have neither: they just serve whatever tools/list returns today. Rename a
tool, add a required argument, narrow an enum — every agent built on your server breaks, and
nothing in your pipeline noticed.
mcp-covenant is one static binary that snapshots your server's interface into a committed
lockfile and fails CI when a change would break existing clients — classified the way a
human would: breaking / minor / patch.
```text
$ mcp-covenant check --baseline mcp-covenant.lock -- node dist/server.js
mcp-covenant: 3 change(s) — required version bump: MAJOR
BREAKING (2)
x tool:legacy — tool was removed [tool.removed]
x tool:search → inputSchema.properties.limit — new required property [schema.property.required.added]
MINOR (1)
+ tool:newtool — new tool [tool.added]
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