MCP Inspector is a developer tool for inspecting Model Context Protocol (MCP) servers. One package, @modelcontextprotocol/inspector, ships three clients behind a single mcp-inspector binary: a web application built with Vite, React, and Mantine on a Node backend; a scriptable command-line client for automation, continuous integration, and fast agent feedback loops; and an interactive terminal interface built with Ink. The web interface is the default, with --cli and --tui selecting the others.
The repository holds the version 2 line. Development happens on the v2/main branch and merges into main at milestone releases, which publish to the npm latest tag, while version 1 receives security fixes only from v1/main under the v1-latest tag. A migration guide covers the version 1 to version 2 changes: remapped command-line flags, the split between --config and --catalog, the Node engine bump to 22.19 or newer, and renamed environment variables.
Version 2 is deliberately not an npm workspace. Each client under clients/ keeps its own manifest and dependencies, shared code lives in core/ and is consumed through an @inspector/core build-time alias, and every runtime dependency that core/ imports is declared once at the repository root. Composable test servers with fixtures back the integration and smoke tests, and the quality gate layers a fast validate loop, a per-file 90 percent coverage threshold, and a local:gate command that is a strict superset of the continuous integration checks.
Project rules live in AGENTS.md and apply to human and AI contributors alike, with multi-step procedures kept as ordinary Markdown skill files under .claude/skills/. All work is issue-driven against the version 2 project board, and outside contributions are accepted as issues rather than pull requests.
Features
- Three clients, one binary: web, command-line, and terminal interfaces dispatched by a shared launcher
- Web application: a Vite, React, and Mantine single-page app with a Node backend for interactive inspection
- Scriptable CLI: a command-line MCP client aimed at automation, CI, and agent feedback loops
- Terminal interface: an Ink-based interactive TUI for terminal-only environments
- Server configuration: --config and --catalog select which server or servers the inspector connects to
- Docker image: a container image with documented ports, volumes, and secret handling
- Test servers: composable MCP test servers and fixtures cover each protocol feature for integration and smoke tests
- Quality gate: a fast validate loop, a per-file 90 percent coverage threshold, and a local gate that supersets CI
- App review recipe: a CLI-first, one-shot-web procedure for automated MCP App tool review
- Version 1 migration guide: flag mapping, config split, Node engine bump, and environment variable renames
