Model Context Protocol (MCP) is an open standard by Anthropic that lets AI assistants like Claude connect to tools and data sources. It's used in Claude Desktop, Cursor, and other AI-powered IDEs.

Where is my MCP config file?

On macOS: ~/Library/Application Support/Claude/claude_desktop_config.json for Claude Desktop. In Cursor: ~/.cursor/mcp.json. Check your app's documentation for the exact path.

What does stdio vs sse vs http mean?

stdio: the MCP server runs as a subprocess. sse: connects to a Server-Sent Events endpoint. http: connects to an HTTP endpoint. Most community MCP servers use stdio.

MCP Config Validator

Runs in browser

Validate MCP server configs with instant error and warning feedback.

Validate Model Context Protocol (MCP) server configuration files in real time. Catches JSON errors, missing keys, invalid types, duplicate names, bad URLs, and sensitive credential warnings.

MCP Config JSON

✓ Valid

Warnings

⚠

mcpServers.github.env.GITHUB_PERSONAL_ACCESS_TOKEN

"GITHUB_PERSONAL_ACCESS_TOKEN" looks like a sensitive credential — avoid committing real tokens. Use environment variables or a secrets manager.

Schema Reference

Field	Type	Required	Description
mcpServers	object	Yes	Map of server name → server config
command	string	or url	Executable to run (stdio transport)
url	string	or command	HTTP/SSE endpoint URL
type	"stdio"\|"sse"\|"http"	No	Transport type (optional, inferred)
args	string[]	No	Arguments passed to the command
env	Record<string,string>	No	Environment variables for the server

🔒 Runs in your browser · No uploads · Your data never leaves your device

How to use

Paste your config
Paste your MCP config JSON into the editor. Validation runs automatically as you type.
Fix errors
Errors (red) must be resolved for the config to work. Each error shows the exact field path and a plain-English explanation.
Review warnings
Warnings (yellow) flag potential issues like hardcoded credentials in env fields — these won't break MCP but indicate security risks.
Apply auto-fix
If an auto-fixable issue is detected (like a missing mcpServers wrapper), click 'Apply Fix' to correct it automatically.

Common use cases

Catching JSON errors before loading Claude Desktop — Paste your config to find syntax errors and missing required keys before your app fails to start.
Detecting hardcoded credentials — Warnings flag tokens and passwords placed directly in env fields — reminding you to move them to a secrets manager.

Examples

Valid filesystem server config
npx-based MCP server for local filesystem access
Output
```
✓ Valid — no issues found
```
Missing mcpServers key
Config with servers at root level instead of inside mcpServers
Output
```
1 error: Missing required key mcpServers. Auto-fix available.
```

Frequently asked questions

What is MCP?: Model Context Protocol (MCP) is an open standard by Anthropic that lets AI assistants like Claude connect to tools and data sources. It's used in Claude Desktop, Cursor, and other AI-powered IDEs.
Where is my MCP config file?: On macOS: ~/Library/Application Support/Claude/claude_desktop_config.json for Claude Desktop. In Cursor: ~/.cursor/mcp.json. Check your app's documentation for the exact path.
What does stdio vs sse vs http mean?: stdio: the MCP server runs as a subprocess. sse: connects to a Server-Sent Events endpoint. http: connects to an HTTP endpoint. Most community MCP servers use stdio.

Key concepts

MCP config: A JSON file specifying MCP server names, commands, arguments, and environment variables for Claude Desktop or Cursor.
Linting: Static analysis of configuration or code to catch errors and bad practices without running it.

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