MCP Config Validator
🔒 In your browserValidate an mcp.json / claude_desktop_config.json and catch common mistakes.
How it works
Paste a claude_desktop_config.json or mcp.json and get instant checks — valid JSON, correct structure, missing command/args, hard-coded secrets and common mistakes. Runs entirely in your browser.
Structural and best-practice checks only — a valid file doesn't guarantee the server itself is safe. To vet what a server can do, use the MCP Security Scanner. Your config is never uploaded.
About the MCP Config Validator
A single misplaced comma or a missing command field will stop an MCP server from loading — often with no clear error. This free MCP config validator checks your claude_desktop_config.json or mcp.json for valid JSON, the right structure, and the mistakes that most commonly break MCP servers.
Your config is checked entirely in your browser and never uploaded, so any keys it contains stay private.
What it checks
- Valid JSON — with a clear pointer to trailing commas, comments or unquoted keys that break parsing.
- Structure — a top-level mcpServers object (or VS Code's servers object) containing one entry per server.
- Each server — a command (stdio) or url (remote), args as an array of strings, and env as string values.
- Common mistakes — npx without -y that can hang, both command and url set at once, and unknown keys.
- Hard-coded secrets — env values that look like real API keys, which shouldn't live in a committed file.
Why MCP servers silently fail
MCP config must be strict JSON — no comments, no trailing commas. Editors that accept JSON5 or JSONC hide these problems until the client refuses to load. Beyond syntax, the most frequent issues are a missing command, args written as a single string instead of an array, and non-string environment values. This validator catches all of those before you restart the client.
Frequently asked questions
Why does my MCP server not show up?
The usual causes are invalid JSON (a trailing comma or comment), a missing or misspelled command, args written as a string instead of an array, or the wrong top-level key. Paste your config here to see which applies.
Can I use comments in an MCP config?
No. Despite what some editors allow, MCP config files are parsed as strict JSON, which doesn't permit // or /* */ comments. Remove them or the file won't load.
Does a valid config mean the server is safe?
No — this only checks that the file is well-formed and sensible. To assess what a server can actually do, use the MCP Security Scanner, which looks for tool poisoning and exfiltration risks.
Is my config uploaded?
No. Validation runs entirely in your browser, so API keys or tokens in the file never leave your device.
Does it support VS Code's format?
Yes. VS Code nests servers under a servers key (with a type field) rather than mcpServers; the validator recognises both and tells you which it found.
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Copy this and paste it into your page's HTML. The tool runs in the visitor's browser, just like here. Change height to fit, or add the optional auto-resize snippet below. Add ?theme=dark to the URL for dark mode.
<iframe src="https://toolhq.dev/embed/mcp-config-validator/" title="MCP Config Validator — ToolsHub" width="100%" height="520" style="border:1px solid #e5e7eb;border-radius:12px;max-width:680px" loading="lazy"></iframe>Optional: auto-resize the iframe height
Add this once on the same page so the iframe grows to fit the tool:
<script>
addEventListener("message", function (e) {
if (e.data && e.data.type === "toolshub:resize") {
document.querySelectorAll('iframe[src*="/embed/"]').forEach(function (f) {
if (f.contentWindow === e.source) f.style.height = e.data.height + "px";
});
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});
</script>