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Open-source · Python · ESLint for MCP Schemas

Grade Your MCP Tool Schemas A+ to F

The only build-time quality linter for MCP. Validate, audit tokens, optimize, auto-fix, grade. Try it now — Notion scored F.

5
CLI Commands
5
LLM Providers
3759
Tests
MIT
License

Try it now — no install

Tools that run in your browser. No account, no API key.

🛠️ MCP Developer Toolkit

Five tools covering the full MCP developer lifecycle: lint → secure → test → debug → deploy-gate.

Schema linter + token auditor. 69 checks. Grade A+ to F. Auto-fix issues. 201 MCP servers benchmarked.
pip install agent-friend
$ agent-friend grade server.json Grade: A+ (96.0) 69 checks 0 issues $ agent-friend fix server.json # auto-fix
AST-level security scanner. Finds shell injection, path traversal, SSRF in MCP tool source code before deployment.
pip install mcp-patch
$ mcp-patch scan server.py CRITICAL shell_injection line 12 HIGH ssrf line 34
pytest fixture for MCP servers. Spin up a real server, call tools, assert results. No mocking required.
pip install mcp-pytest
def test_search(mcp_server): result = mcp_server.call("search", query="test") assert result["results"]
Transparent stdio interceptor. See every JSON-RPC message between host and server in real-time. Zero deps.
pip install mcp-snoop
$ mcp-snoop -- python3 server.py initialize {"protocolVersion": "2024-11-05"} tools/list [{"name": "search", ...}]
Schema lockfile + breaking change detector. CI gate that fails when tool signatures change unexpectedly.
pip install mcp-diff
$ mcp-diff lock server.json # save snapshot $ mcp-diff check server.json # CI: detect drift BREAKING search: param "limit" removed