What is the MCP Inspector?

The MCP Inspector tests an MCP server on its own, before you connect it to Claude or ChatGPT.

The MCP Inspector is the official tool for testing an MCP server. It lists the server's tools, lets you run them with test inputs, and shows the messages that go back and forth.

Also called MCP Inspector tool, MCP tester, MCP test tool, modelcontextprotocol inspector, npx @modelcontextprotocol/inspector.

The Inspector comes from the MCP project itself. It is one npm package, @modelcontextprotocol/inspector, with three ways to use it: a web page in your browser, a command-line client for scripts and CI, and a terminal screen for when you have no browser.

You do not install it. Run it with npx and point it at the server you want to check. It needs Node 22.19.0 or newer.

npx @modelcontextprotocol/inspector            # web UI
npx @modelcontextprotocol/inspector --cli      # command line
npx @modelcontextprotocol/inspector --tui      # terminal screen

The Inspector is a developer tool. It talks to a server directly, without Claude or ChatGPT in the middle, so you can tell whether a problem is in the server or in the assistant.

Related:MCP serverMCP tools Model Context Protocol (MCP)

The MCP Inspector is the official tool for testing and debugging an MCP server. Start it with one npx command, point it at a server, then list its tools, run them and read the raw messages. Use the web version to explore, the CLI version for scripts and CI, and the terminal version when no browser is available.

The one thing to know first: the Inspector stores OAuth tokens and secrets. It uses your computer's keychain when there is one. On a machine without a keychain (a Linux server, an SSH session, a container) it writes them to ~/.mcp-inspector/secrets.json unencrypted unless you set a key.

To inspect a server that runs from a package, pass the launch command after the Inspector command, for example npx @modelcontextprotocol/inspector uvx mcp-server-git --repository ~/code/mcp/servers.git. For a hosted server, use --server-url https://api.example.com/mcp --transport http. Always read the server's own README first, because every server takes different arguments.

Good for

Developers building an MCP server who want to see every tool work
Anyone debugging a connector that fails in Claude or ChatGPT
Teams checking a server in CI before release
Careful users who want to see what a server offers before trusting it

Comparison

Start with the web client, which is the default and the richest. Use the CLI when a script, CI job or coding agent needs to check a server and read the result as JSON.

Option	Flag	Needs browser	Best for
WebThis page	None (default)	Yes	Exploring
CLI	--cli	No	Scripts and CI
TUI	--tui	No	Terminal only

Questions

What is the MCP Inspector?

The official tool for testing and debugging MCP servers. It runs in your browser, on the command line or in a terminal screen, and lets you list a server's tools, call them and see the messages exchanged.

How do I run the MCP Inspector?

Run npx @modelcontextprotocol/inspector in a terminal. It prints a link with a per-launch token and opens it in your browser. You need Node 22.19.0 or newer, and nothing to install.

How do I test my own MCP server with it?

Add the command that starts your server after the Inspector command, for example npx @modelcontextprotocol/inspector node path/to/server/index.js. For a hosted server, use --server-url with the address and --transport http.

Does it work with remote MCP servers?

Yes. Point it at the server's web address with --server-url and --transport http, or add the server from inside the web page.

Can I use the Inspector in CI?

Yes. The CLI client lists tools and calls them from a script, and --format json gives output you can pipe into jq. The Inspector docs also describe exit codes for pass and fail checks.

Is the MCP Inspector the same as a Claude connector?

No. A connector is a server added to Claude. The Inspector is a separate tool that talks to the server directly, so you can check the server before you add it. See what a connector is.

Is it safe to use?

It runs on your own computer. It does store OAuth tokens and secrets, in your keychain when one exists, otherwise in a plain file under ~/.mcp-inspector/. Check the storage notes before using it on a shared or headless machine.

Which version should I use, v1 or v2?

Use the current one that npx @modelcontextprotocol/inspector gives you. The older v1 line only gets security fixes and is available as @modelcontextprotocol/inspector@v1-latest.

Sources

Docs, issue trackers and discussions this page is built from.

Show all 2

MCP Inspector · modelcontextprotocol.io
modelcontextprotocol/inspector README · github.com