Developer Tool

MCP Tool Schema Checker

Check MCP tool definitions and input/output JSON Schema structure locally, with errors and explicit limits.

✅ Free access 🔒 No Signup ⚡ Browser processing 🌐 Browser Based

Quick Answer

Check MCP tool definitions and input/output JSON Schema structure locally, with errors and explicit limits.

Local checks only. Input is not submitted to a server. No model calls, command execution or server connections. Limit: 100,000 characters, 40 nesting levels and 100 tools/servers. Background processing stops after 3 seconds.

MCP tool definition or tools/list JSON

Quick Facts

Tool Name: MCP Tool Schema Checker
Category: Developer Tool
Price: Free local checks; 100 definitions, 100,000 characters and a 3-second processing limit.
Platform: Browser Based
Login Required: ✓ No
Last updated: 2026-10-15
Processing & privacy: The core calculation runs in your browser. This tool does not need a paid AI API for its core output.
Scope: Results describe the submitted input and supported checks. They do not guarantee accuracy, search rankings, indexing or AI citations. Read our testing and scoring methodology.

How to Use MCP Tool Schema Checker

Enter Your Input
Paste your text or fill in the required fields in the tool above.
Run the Tool
Use the controls above; some browser tools update as you type.
Review the Results
Review the output and any warnings. Hosted checks need an internet connection.
Copy or Export
Use the available copy or download controls, and review suggestions before publishing.

How to use the MCP Tool Schema Checker

Paste one tool definition, an array of tools, a tools/list result or its JSON-RPC response. Run checks and inspect field paths in the report.

Supported checks and limits

Checks tool names, duplicate names, metadata types, schema meta-schema validity and selected annotation types. References are not resolved; patterns, formats and sample payloads are not executed. Unknown schema extension keywords may be allowed by the meta-schema. Other MCP fields and protocol versions are not certified.

Up to 100,000 characters and 40 nesting levels. Tool/configuration checks accept up to 100 definitions. Processing stops after three seconds and reports at most 200 findings. YAML aliases and shared objects are unsupported.

Reference and version

MCP 2025-11-25; JSON Schema 2020-12 and draft-07. Read the official reference. Newer specifications or client extensions may differ.

Privacy and report handling

The validator runs locally and does not execute pasted instructions or commands. It does not save inputs to browser storage. Review field names in exported reports before sharing.

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Frequently Asked Questions

Everything you need to know about MCP Tool Schema Checker

What does this tool check?

Does it use a paid API or upload my input?

No. Validation runs in a browser worker. This tool does not submit the pasted input or call an AI model.

Does a clean report guarantee compatibility or security?

No. It means no errors were found in the checks performed. Review warnings, the documented scope and the target client or protocol documentation.

Can I download the results?

Yes. Download a JSON report containing finding paths, messages and scope. It excludes input values, but field names can still contain sensitive information.

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