MCP config validator
Paste your mcpServers config and it's checked instantly — the validator catches the silent killers MCP clients fail on without telling you (a trailing comma, smart quotes, wrong nesting, unescaped Windows paths), points at the line, and formats the result. Everything runs in your browser.
Paste your mcpServers config — it's checked instantly, nothing leaves your browser.
What does the MCP config validator check?
It separates JSON parsing failures from MCP-specific structure problems. That distinction matters: malformed JSON prevents the client from reading the file at all, while a valid document with the wrong shape can load without creating a usable server connection.
| Check | Problem it finds | What to do next |
|---|---|---|
| JSON syntax | Trailing commas, smart quotes, or missing brackets | Fix the reported line, then validate again |
| Top-level shape | Missing or misplaced mcpServers object | Move named servers under one mcpServers key |
| Server entries | A local server without a command or a remote server without a URL | Add the transport fields required by that client |
| Common path hazards | Unescaped Windows backslashes and misplaced environment values | Use valid JSON escaping and keep secrets inside env |
How do you validate an MCP configuration safely?
Paste the exact configuration your client reads, correct the first reported error, and run the validator again until the document passes. Then test one server at a time in the client; a valid document does not prove that a package exists, a remote endpoint is reachable, or a credential has permission.
- Make a backup of the client's current config file.
- Remove real secret values if you plan to share a screenshot or error report.
- Paste the complete JSON here and fix syntax before changing commands or credentials.
- Copy the formatted result back to the correct client-specific file.
- Restart the client and inspect the server process logs if the connection still fails.
Need a clean starting file? Build one with the MCP config generator. Moving between clients? Use the config converter before validating the destination format. For a share-safe diagnostic copy, redact secrets with the MCP config redactor.
FAQ
Why does my MCP config fail with no error?
MCP clients parse the config silently — a syntax error just makes them load nothing instead of showing a message. This validator surfaces the exact error (and line) so you can see what the client won't tell you.
Is my config sent anywhere?
No. The validator runs entirely in your browser — your config and any API keys in it never leave your machine.
What's the correct mcpServers structure?
{ "mcpServers": { "name": { "command": "npx", "args": ["-y", "package"], "env": { "KEY": "value" } } } } — one top-level mcpServers object, no trailing comma after the last entry.
What if the JSON is valid but the server still will not connect?
Valid JSON only proves the file can be parsed. Next check the client-specific file location, command or URL, executable PATH, environment variable names, and the server process logs.