@baichen_yu/mcp-guard

v0.3.2

Published

a month ago

Security auditing and policy gating for MCP servers (STDIO/HTTP) with Markdown + SARIF reports

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baichen_yu

mcp model-context-protocol security audit sarif cli lint

mcp-guard

Security auditing and policy gating for MCP servers (local + CI).
Deterministic checks. Actionable findings. Reproducible reports.

[!IMPORTANT] Remote mode supports HTTP JSON-RPC (--http) and SSE (--sse, optional --sse-post).

Why people use mcp-guard

✅ Deterministic contract tests (no fuzzy behavior, no mystery calls)
✅ Policy gate in CI (--fail-on off|low|medium|high)
✅ Security-focused rule packs with profile controls (default, strict, paranoid)
✅ Review-friendly output formats (report.md, report.json, report.sarif)
✅ Config discovery + redaction for common MCP client config layouts

Quick stats

| Signal | Value | |---|---:| | Transports | STDIO + HTTP JSON-RPC + SSE | | Report formats | Markdown, JSON, SARIF | | Rule profiles | 3 | | Contract scenarios | list, call, error shape, cancellation behavior, large payload, timeout | | Registry modes | lint, verify, score |

30-second quickstart

1) No install (`npx`)

npx @baichen_yu/mcp-guard audit \
  --stdio "node /absolute/path/to/your-mcp-server.cjs" \
  --out reports \
  --fail-on off

[!TIP] --stdio runs in your current working directory. Use an absolute path or cd into the project that contains your server first.

Local demo (from this repo root)

npm run fixtures:gen
npx @baichen_yu/mcp-guard audit \
  --stdio "node fixtures/servers/hello-mcp-server/server.cjs" \
  --out reports \
  --fail-on off

2) Global install

npm i -g @baichen_yu/mcp-guard
mcp-guard --help

3) Package + command naming

npm package: @baichen_yu/mcp-guard
runtime CLI command: mcp-guard
first scoped publish command: npm publish --access public

Architecture

flowchart LR
  CLI[mcp-guard CLI] --> T[Transport layer\nSTDIO HTTP SSE]
  T --> RPC[JSON-RPC client]
  RPC --> TESTS[Contract tests]
  RPC --> RULES[Rules and profiles]
  TESTS --> REPORTS[Reports\nMD JSON SARIF]
  RULES --> REPORTS
  REPORTS --> GATE[Policy gate fail-on]
  GATE --> CI[CI and code scanning]

Audit pipeline

flowchart TD
  A[Start audit] --> B[Initialize session]
  B --> C[List tools]
  C --> D[Run contract suite]
  C --> E[Run schema and security rules]
  D --> F[Apply profile tuning]
  E --> F
  F --> G[Compute score]
  G --> H[Emit reports]
  H --> I[Exit by policy threshold]

Report preview

# MCP Guard Report
- Risk score: 100/100
- Key findings: 0
- Contract tests: 6/6
- Target: node fixtures/servers/hello-mcp-server/server.cjs (stdio)

Commands

# Validate / Test / Audit
mcp-guard validate --stdio "node server.cjs" --profile default --out reports
mcp-guard test --stdio "node server.cjs" --out reports
mcp-guard audit --stdio "node server.cjs" --profile strict --fail-on medium --sarif reports/report.sarif

# Remote audit (HTTP JSON-RPC)
mcp-guard audit --http "http://127.0.0.1:4010" --timeout-ms 30000 --fail-on off

# Remote audit (SSE stream + POST endpoint)
mcp-guard audit --sse "http://127.0.0.1:4013/sse" --sse-post "http://127.0.0.1:4013/message" --timeout-ms 30000 --fail-on off

# Config scan
mcp-guard scan --repo . --format md --out reports

# Registry checks
mcp-guard registry lint registry/servers.yaml
mcp-guard registry verify registry/servers.yaml --sample 5
mcp-guard registry score registry/servers.yaml

CI integration (drop-in)

jobs:
  mcp-audit:
    runs-on: ubuntu-latest
    permissions:
      security-events: write
      actions: read
      contents: read
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - uses: ./.github/actions/mcp-guard
        with:
          stdio_command: node fixtures/servers/hello-mcp-server/server.cjs
          fail_on: high

Automated releases

On each push to main, .github/workflows/release.yml now:
- runs lint/test/build
- computes the next available version above local and npm latest
- builds release assets (package tarball + compiled dist archive)
- creates/updates a GitHub Release with GitHub generated (auto/AI-style) release notes + uploaded assets
- publishes the new package to npm (requires NPM_TOKEN)
For npm publishing in CI, set NPM_TOKEN to an npm Automation token (no interactive password/OTP required).

Docs site (GitHub Pages)

URL pattern: https://<owner>.github.io/mcp-guard/
Current docs: https://tomas-1226.github.io/mcp-guard/
One-time setup: Settings → Pages → Source → GitHub Actions

Troubleshooting

Run npm publish from the project root (the directory containing package.json).

Confirm endpoint supports JSON-RPC via HTTP POST and increase --timeout-ms if startup is slow.

Wrap --stdio values in double quotes.

Release helper

Build release artifacts locally/offline (after one online npm ci):

npm run release:offline

License

MIT. See LICENSE.

npm package run check

npm run npm:test-run