mcp-check-fixture

The MCP server MCPJam's GitHub PR checks are validated against. This directory is the seed for the standalone public repository mcpjam/mcp-check-fixture — the only repo the walking-skeleton check pipeline is wired to (server/services/github-checks/recipes.ts).

It lives here so it is reviewed alongside the pipeline that depends on it, and so the ops step is "copy and push" rather than "write from scratch".

Publishing it

cp -R test-servers/mcp-check-fixture /tmp/mcp-check-fixture
cd /tmp/mcp-check-fixture
git init && git add -A && git commit -m "mcp-check-fixture: minimal MCP server"
gh repo create mcpjam/mcp-check-fixture --public --source=. --push

package-lock.json is committed here on purpose, and must stay committed in the published repo: the run recipe uses npm ci, which fails outright without one. A repo missing its lockfile reports build_failed — correctly, but confusingly. @types/node is likewise a real devDependency, not an assumption about the build environment: tsconfig.json declares "types": ["node"], and this package is standalone with no workspace to hoist it from.

Related MCP server: mcpscope

The two things that must not be "cleaned up"

It binds 0.0.0.0, not 127.0.0.1. E2B's host bridge only forwards to ports bound on all interfaces. A loopback-only server is invisible from outside the sandbox and the check reports server_unhealthy with a stderr tail that may not mention the bind address at all.

It answers initialize on /mcp immediately. That handshake is the health probe — the worker polls it until it succeeds. Anything that delays it (a warm-up, a lazily mounted route) reads as an unhealthy server.

Run recipe

The recipe hardcoded in the Inspector for this repo:

Changing any of those means changing recipes.ts in the same breath.

Tools

Three, all deterministic and side-effect-free — the eval suite's job is to prove the pipeline works, not to be an interesting test:

• echo({ text }) → the same text

• add({ a, b }) → the sum

• server_info() → {"name":"mcp-check-fixture","version":"1.0.0"}

Locally

npm install && npm run build && npm start
curl -s localhost:3001/mcp -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"curl","version":"1"}}}'

Exercising the check's failure modes

Each of these is a one-line change, and each should produce a specific check conclusion — useful for verifying the pipeline end to end: