JSON syntax and root structure
Detects parse failures, missing mcpServers, incorrect container types, trailing commas, comments, and common property-name mistakes.
Private MCP JSON checker
Fix your MCP config before the next restart.
MCP Config Validator checks Claude Desktop, Cursor, and VS Code configuration for JSON syntax, mcpServers, command, URL, transport, args, and environment errors—entirely in your browser.
Free · No account or email · Your configuration never leaves this device
Claude Desktop
Cursor
VS Code
Generic MCP JSON
LOCAL VALIDATION
Configuration health
Errors become next steps
Free, no sign-upUse the full validator immediately
Browser-only processingNo config or secret is uploaded
Major MCP clientsClient-aware paths and checks
Actionable reportDownload fixes as Markdown
MCP configuration checker
Validate Claude Desktop or Cursor MCP JSON
Paste or upload a configuration file. The checker parses its structure, reviews each server, suggests safe corrections, and creates a reusable diagnostic report.
1. Add your configuration
JSON
Typical path: ~/Library/Application Support/Claude/claude_desktop_config.json
or paste JSON
Ready to validate the sample configuration.
2. Review diagnostics
NOT CHECKED
0Errors
0Warnings
0Servers found
Run the validator to see syntax, structure, and server-level findings.
-
Your config stays private
Parsing, validation, repair suggestions, and report generation happen inside this page.
What the validator checks
From invalid JSON to a runnable MCP server
A syntactically valid file can still fail at runtime. These checks cover both the document and the server definitions inside it.
stdio command, args, and env
Reviews executable commands, argument arrays, environment objects, empty values, shell-dependent patterns, and accidental secret exposure.
HTTP and SSE server URLs
Checks URL validity, protocol safety, conflicting command and URL fields, transport hints, localhost endpoints, and unsupported field combinations.
Practical MCP config examples
Common Claude Desktop and Cursor MCP errors
Use these input → diagnosis → fix examples to narrow down why an MCP server is not appearing, starting, or connecting.
“Expected property name” JSON error
A trailing comma makes the complete configuration unreadable.
{
"mcpServers": {
"docs": {
"command": "npx",
"args": ["-y", "server"],
}
}
}
Fix: remove the comma after the args array. Standard JSON does not allow trailing commas or comments.
MCP server command not found
The JSON parses, but the client cannot resolve a shell alias or relative executable.
{
"mcpServers": {
"local": {
"command": "my-server",
"args": []
}
}
}
Fix: use an installed executable or an absolute path. GUI apps may not inherit the same PATH as your terminal.
Remote MCP URL and transport conflict
A server definition should not mix a local stdio command with a remote URL.
{
"mcpServers": {
"api": {
"command": "node",
"url": "https://example.com/mcp"
}
}
}
Fix: choose one connection model: command with optional args, or a valid HTTP(S) url.
How to check MCP configuration
Three steps from config to clear repair plan
Paste or upload JSON
Select the client and operating system so the page can show the relevant configuration path and context.
Review each finding
Errors identify blockers. Warnings flag values that are legal but likely to fail or expose sensitive information.
Download and retest
Save the Markdown repair report, apply changes carefully, restart the MCP client, and validate the updated file again.
MCP configuration FAQ
Questions developers ask before restarting the client
Where is the Claude Desktop MCP config file?
On macOS, the typical path is ~/Library/Application Support/Claude/claude_desktop_config.json. On Windows, it is commonly %APPDATA%\Claude\claude_desktop_config.json. Paths can change by client version, so verify them against your installed client if the file is absent.
Why is my MCP server not showing in Claude Desktop?
Frequent causes include invalid JSON, a missing mcpServers object, an executable unavailable to the GUI app, incorrect arguments, or failure to restart the client after editing. Validate the file first, then launch the command directly in a terminal to isolate runtime problems.
How do I validate a Cursor MCP configuration?
Select Cursor above, paste the complete JSON, and run the checker. It validates the same core server fields while showing Cursor-specific path guidance. Always test the exact file used by the workspace or user-level configuration.
Can an MCP config use both command and URL?
A single server definition generally represents either a local stdio process using command and args, or a remote endpoint using url. Mixing both is ambiguous, so this validator reports it as an error.
Is it safe to paste environment variables here?
The validator works locally and does not send the configuration to a server. Even so, avoid sharing screenshots or copied reports containing real tokens. The downloaded report redacts values whose names look like passwords, secrets, tokens, or API keys.
Does this tool confirm that an MCP server is reachable?
No. Browser security and the local-only design mean it performs static configuration validation, not command execution or network probing. A clean result confirms the checked structure and values, not server availability or package installation.
How do I fix trailing commas or comments in MCP JSON?
Remove the comma after the final property in each object or array, and delete // or block comments. JSON requires double-quoted property names and strings. The parser result points near the first syntax error it encounters.
Keep the diagnosis
Take an MCP repair checklist into your next debugging session.
Download a Markdown file containing the current client, configuration path, redacted config, diagnostics, and prioritized next steps.
Free · No registration · Generated locally · A useful sample template is included if you have not run a check