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MCP Schema Validator — Free Model Context Protocol Tool Online | DevFlow

MCP Schema Validator

Validate, format, and debug MCP (Model Context Protocol) server schemas.

A free browser-based validator for Model Context Protocol (MCP) 2024-11 schemas. Instantly check tool definitions, validate JSON Schema input schemas with AJV Draft 07, verify tool naming conventions, and generate server summaries. All processing happens client-side — your MCP server data never leaves your browser.

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Tags: mcp, model context protocol, schema, validate, ai, agent, tool, json schema, anthropic, claude, cursor

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How to MCP Schema Validator Online

  1. Paste your MCP (Model Context Protocol) schema into the input area. The tool automatically detects whether you are using JSON or YAML format.

  2. Click the Validate button or press ⌘⇧V (Mac) / Ctrl+Shift+V (Windows) to instantly check your schema against MCP 2024-11 specification rules.

  3. Review the detailed Issues panel for any errors or warnings. Each issue shows the severity level, exact path (e.g., tools[0].name), and a descriptive fix message.

  4. Click Format to safely parse and rebuild your MCP schema with clean, consistent indentation in JSON or YAML.

  5. Click Summary to generate a high-level overview of your MCP server — including protocol version, tool count, capabilities, and server info.

  6. You can toggle 'Auto Validate' to run checks instantly as you type. Use the Share button to generate a compressed URL for your team.

MCP Schema Validator Features

  • Comprehensive MCP schema validation — Checks tool names, input schemas, capabilities, serverInfo, and protocolVersion against the official MCP 2024-11 specification.

  • AJV-powered JSON Schema validation — Validates each tool's inputSchema using AJV with Draft 07 support and built-in format validators (email, URI, date, etc.).

  • Intelligent format detection — Automatically identifies whether your input is JSON or YAML and handles both seamlessly.

  • Bidirectional format conversion — Format your MCP schema in JSON or YAML with configurable indentation (2, 4, or 8 spaces).

  • Detailed issue reporting — Every validation error shows severity (ERROR / WARNING), the exact object path, and an actionable message explaining the fix.

  • Server summary generation — Instantly extracts protocol version, server name, tool count, capabilities (tools, resources, prompts), and tool descriptions into a readable summary.

  • Tool name validation — Ensures all tool names conform to the strict MCP naming convention (^[a-zA-Z0-9_-]+$), catching invalid characters early.

  • Input schema integrity checks — Verifies that every tool's inputSchema is a valid JSON Schema object, not a string or primitive.

  • Real-time auto-validation — Toggle auto-validate to get instant feedback as you type your MCP schema.

  • Shareable URLs — Generates gzip-compressed URL parameters so you can safely share MCP schemas with teammates.

  • Client-side execution — All validation happens in your browser. Your MCP server schemas and tool designs never leave your device.

  • Developer keyboard shortcuts — ⌘⇧V to validate, ⌘⇧F to format, ⌘⇧S for summary, ⌘⇧C to copy output, ⌘⇧K to clear.

Frequently Asked Questions

What is the Model Context Protocol (MCP)?
The Model Context Protocol (MCP) is an open standard developed by Anthropic that enables AI assistants (like Claude, Cursor, and others) to connect to external data sources and tools. An MCP server exposes a set of tools via JSON-RPC, each with a name, description, and JSON Schema input definition. This protocol allows AI models to discover and invoke capabilities dynamically.
What does this MCP Schema Validator check?
This validator checks your MCP server schema for structural correctness against the MCP 2024-11 specification. It validates: required fields (schema, protocolVersion, capabilities, serverInfo), tool name formatting (must match ^[a-zA-Z0-9_-]+$), inputSchema validity (must be valid JSON Schema Draft 07), capabilities structure (must be an object), and overall JSON/YAML parseability.
Does this tool support both JSON and YAML?
Yes. The validator automatically detects whether your input is JSON or YAML. You can paste a JSON MCP schema and format it as YAML, or vice versa. The tool uses the same parsing engine as our YAML Converter for reliable multi-document and anchor support.
Is my MCP schema data safe?
Absolutely. All validation, formatting, and summary generation happens entirely in your browser using client-side JavaScript. Your MCP server schemas, tool definitions, and proprietary API designs are never transmitted to any server, cloud service, or third party.
What MCP specification version is supported?
This tool validates against the MCP 2024-11-05 specification (the stable release). It checks for required fields like schema, protocolVersion, capabilities, serverInfo, and tools as defined in the official MCP schema.
Why does my MCP tool name fail validation?
MCP tool names must match the regular expression ^[a-zA-Z0-9_-]+$ — meaning only letters, numbers, underscores, and hyphens are allowed. No spaces, periods, or special characters. Common fixes: replace 'get weather' with 'get_weather', 'user.list' with 'user_list', or 'fetch-api' (if it already matches, keep it).
What is a valid MCP inputSchema?
An MCP inputSchema must be a valid JSON Schema object (Draft 07) that defines the parameters your tool accepts. It should include a 'type' key (usually 'object'), 'properties' describing each parameter, and optionally 'required' listing mandatory fields. The validator uses AJV with format support to compile and verify your schema.
How do I debug MCP schema validation errors?
Run the Validate action and review the Issues panel. Each error shows: severity (ERROR or WARNING), the exact path in your schema (e.g., tools[0].inputSchema), and a descriptive message. Fix errors from top to bottom since later issues may be caused by earlier ones. Use the Format action to standardize indentation and spot syntax issues.
Can I use this to validate an MCP server before deploying?
Yes. Paste your MCP server's tools/list response or initialization result into the validator before deployment. This catches schema issues, invalid tool names, malformed input schemas, and missing required fields before your server ever connects to Claude, Cursor, or another MCP client.
What is the difference between Validate and Summary?
Validate checks your schema for errors and displays a pass/fail result with detailed issue listings. Summary parses a valid schema and generates a human-readable overview — showing your server name, protocol version, number of tools, capabilities (tools/resources/prompts), and a list of available tools with descriptions.

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