Find out why your MCP server will not start.
Paste .mcp.json or claude_desktop_config.json and get the JSON error with its line and column, the schema problems underneath it, and the small mistakes that fail silently.
Runs in your browser. Whatever you drop or paste here is read by JavaScript in this tab and never sent anywhere. There is no upload endpoint on this site to send it to.
Project servers live in .mcp.json at a repository root. Claude Desktop keeps claude_desktop_config.json under ~/Library/Application Support/Claude/. Both use the same mcpServers object.
Common questions
Why does my MCP server not appear at all?
Most often the config file failed to parse, and the tool that read it fell back to having no servers rather than reporting an error. A trailing comma or a // comment is enough — both are ordinary in JavaScript and both are invalid JSON. This page tells you the line and column, which is the part the silent failure withholds.
Where does the config file live?
Project-scoped servers go in .mcp.json at the root of a repository. Claude Desktop reads claude_desktop_config.json from its application support directory. Both use the same mcpServers object, so both validate here.
What shape should a server entry be?
One of two. A local server has a command plus optional args and env — the tool spawns that process and talks to it over stdio. A remote server has a type of http or sse plus a url. An entry with neither, or with both, is the second most common reason a server never registers.
Should API keys go in the config file?
Not as literals. An env value that starts with sk-, ghp-, a long hex string or anything else key-shaped is flagged here, because config files get committed and shared far more casually than the secrets inside them deserve. Reference an environment variable instead and keep the value out of the file.
Does a clean result mean the server will work?
It means the config is well-formed and internally consistent. It cannot tell you whether the command exists on your PATH, whether the URL is reachable, or whether the credential is still valid — those fail at launch, not at parse.
This page validates the one config you paste into it. It cannot see the rest of your Mac — a browser is not allowed to, which is the whole reason this page is safe to use. Inventory is the desktop app that does: it indexes every conversation Cursor, Claude Code, Zed, Codex, Kiro and Antigravity have had on your machine and searches all of them at once, privately, from ⌘⇧Space. $19.99 once, free for 7 days, no account.