modelcontextprotocol/inspector

A developer tool for inspecting Model Context Protocol (MCP) servers. It ships as a single package, @modelcontextprotocol/inspector, that provides four ways to inspect a server:
Web — a Vite + React + Mantine single-page app with a Node backend.
CLI — a scriptable command-line client for automation, CI, and fast agent feedback loops.
TUI — an interactive terminal UI built with Ink.
mcpdo (experimental) — a connection CLI: connect once, then run many commands against the named connection through an implicit local daemon. See clients/mcpdo.
The first three run through one global mcp-inspector binary; mcpdo is a second binary in the same package:
bash
npx @modelcontextprotocol/inspector # web UI (default)
npx @modelcontextprotocol/inspector --cli # CLI
npx @modelcontextprotocol/inspector --tui # TUI
npx -p @modelcontextprotocol/inspector mcpdo --help # mcpdo
> [!WARNING]
> The Inspector manages secrets — OAuth tokens, OAuth client secrets, and stdio env: values — and stores them in the OS keychain, if available, by default. On a machine with no keychain — Linux without libsecret or a Secret Service, headless and SSH sessions, Termux, and containers with a mounted volume — they are saved to ~/.mcp-inspector/secrets.json instead, unencrypted unless you supply a key. See Where secrets are stored for how to get a keychain back, encrypt the file, or keep secrets in memory only.
> Upgrading from v1? Read the v1 → v2 migration guide — CLI flags, the new --config vs. --catalog split, the Node engine bump, and what no longer ships.
> Repo status. This is the v2 line of the Inspector. Active development happens on v2/main (the develop branch — all v2 PRs target it), which is merged into main at milestone releases; main is the default branch and holds the latest released v2, published to the npm latest tag. The legacy v1 line lives on v1/main — security fixes only, published straight from that branch to the npm v1-latest tag (npx @modelcontextprotocol/inspector@v1-latest). See AGENTS.md for branch/board conventions.
## Quick start (development)
Requires Node ^22.23.4 || ^24.22.1 || >=26.12.1: the patched release on each supported line.
bash
npm install # at the repo root; postinstall cascades into every client
npm run build # web → cli → tui → launcher
For day-to-day web iteration, run Vite directly — fast HMR, no launcher build needed:
bash
cd clients/web && npm run dev
The launcher-driven scripts run the built launcher, so build first:
bash
npm run web # prod web launcher against clients/web/dist
npm run web:dev # web launcher in --dev mode (Vite)
v2 is not an npm workspace — each client under clients/ keeps its own package.json and nodemodules, and shared code lives in core/, consumed via a @inspector/core build-time alias. Every runtime dependency core/ imports is declared once, in the repo-root package.json, and each client declares only what that client alone consumes — its UI stack, its bundler-inlined packages, its dev tooling — which leaves clients/cli and clients/launcher with no runtime dependencies of their own. What that means for adding a dependency (root vs. client, dependencies vs. devDependencies, and the bundler external lists) is in the local-dev skill.