MCP Config Validator

Nothing to format yet.

How to use it

1. Paste the contents of your .mcp.json (Claude Code) or claude_desktop_config.json (Claude Desktop) into the box. A sample with a few common mistakes is already there.
2. Read the results list on the right. Errors will stop a server from working. Warnings are likely problems. Notes are things worth knowing, such as which environment variables you need to set.
3. If the JSON itself is broken, the tool tells you the exact line and column. Press "Fix common JSON mistakes" to remove trailing commas and comments and to straighten curly quotes and single quotes.
4. When it looks right, copy the neatly formatted version from the "Formatted config" box.

Everything runs in your browser. The text you paste is not sent to a server, which is the right way to handle a file that can contain tokens.

What an MCP config looks like

MCP (Model Context Protocol) servers give Claude extra tools, like reading files or talking to GitHub. Both Claude Code and Claude Desktop read a JSON file with one top-level key, mcpServers. Inside it, each server has a name and its settings.

A local server runs a program on your machine:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/path/to/folder"],
      "env": { "SOME_KEY": "value" }
    }
  }
}

A remote server in Claude Code's .mcp.json uses a web address instead:

{
  "mcpServers": {
    "docs": {
      "type": "http",
      "url": "https://docs.example.com/mcp",
      "headers": { "Authorization": "Bearer ${DOCS_TOKEN}" }
    }
  }
}

The type can be stdio (local, the default when you give a command), http, or sse. SSE is the older remote style and is deprecated in favour of http. In .mcp.json, Claude Code can fill in environment variables: ${VAR} uses the variable, and ${VAR:-default} falls back to a default when it is not set. This works in command, args, env, url and headers. That is the safe way to keep secrets out of a file you commit.

FAQ

Why does Claude say my MCP server failed to start?

The most common causes are a JSON typo, the wrong top-level key (servers is VS Code's format, Claude needs mcpServers), a whole command typed into command instead of being split into command and args, or a placeholder such as YOUR_API_KEY that was never replaced. This tool checks for all of them.

Why must "args" be a list?

Claude passes each item in args to the program as a separate argument. A single string like "-y some-package" is treated as one argument, so the program does not understand it. Write ["-y", "some-package"] instead.

Why do numbers and true/false in "env" cause errors?

Environment variables are always text. Write "PORT": "5432", not "PORT": 5432.

Should I put my API key straight into the file?

Avoid it for any file that might be committed or shared. In .mcp.json, write "${MY_TOKEN}" and set the variable in your shell. Claude Desktop may not expand variables, so keep that file private on your own machine.

Does this tool check that the server really works?

No. It checks the structure and common mistakes in the file, without running anything. Use /mcp inside Claude Code to see whether each server connects.

If you would rather start from working setups, Agentsforce ships 38 ready-made specialists for Claude Code. This tool is independent and not affiliated with Anthropic.