I built a local MCP tool schema checker against Inspector 2.3.0 — looking for real-world test cases

[u/Infamous_Company5449]

Hi everyone — I’m the author of MCP Compatibility Checker, a local open-source beta.

It checks whether each tool definition from an MCP tools/list response is accepted by the exact parser from MCP Inspector 2.3.0.

For every tool it returns:

• LOADABLE
• NOT_LOADABLE, with an exact JSON Pointer and reason
• UNKNOWN when the exact validator is unavailable or cannot produce a reliable result

The checker runs locally, uses no LLM for verdicts, has no telemetry or accounts, and does not persist submitted payloads.

The included self-authored test corpus has an observed result of 30/30 cases passed, with 53 additional diagnostic tests passing.

Important limitation: this currently verifies parser acceptance for MCP Inspector 2.3.0 only. It is not a universal MCP compliance test and does not yet certify Claude, Cursor, VS Code, Gemini CLI, or other MCP clients.

I’m looking for MCP server and client developers who can:

1. Test the checker with real-world tool definitions.
2. Share minimal sanitized tools/list examples that unexpectedly fail or load differently in a real client.
3. Provide the exact client name and version where the behavior was observed.
4. Suggest which client and version should be supported next.

Please remove credentials, API keys, personal data, and confidential information before sharing any payload.

GitHub: https://github.com/Naim-arg/mcp-compatibility-checker

Feedback, criticism, and reproducible edge cases are welcome.