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MCP Inspector

Tests and debugs MCP servers from a web UI, a scriptable CLI or a terminal UI

Run with npx

npx @modelcontextprotocol/inspector

Copied from the project's docs at github.com/modelcontextprotocol/inspector

Why you'd want it

The Inspector is the reference developer tool from the MCP project for testing and debugging servers. One npx package gives you a web client that shows the JSON-RPC exchange as you call tools, a CLI with JSON output for CI, shell pipelines and coding agents, and a terminal UI; all three share the same transports, config files and OAuth state. It also installs mcpdo, an experimental client that keeps one connection open across many commands.

Best for

  • MCP server authors
  • Smoke-testing MCP servers in CI
  • Letting a coding agent check its own MCP server from the shell

Use it when

You are building or debugging an MCP server and want to list and call its tools directly, interactively or from a script.

Skip it if

You only use MCP servers and never build one. It needs Node 22.19.0 or newer, and on machines without an OS keychain it stores secrets in an unencrypted file unless you supply a key.

Editor's note

This is the v2 line; v1 gets security fixes only and is published as @modelcontextprotocol/inspector@v1-latest.

Related tools

Same category or shared tags, by drop score.

  1. Rank 60

    Repomix

    Devtool

    Packs a repository into one AI-friendly file in XML, Markdown, JSON or plain text

    • score 39
    • 28.8k stars
    • pushed
    • v1.18.1 on
    • MIT

    Run with npx

    npx repomix@latest
    Use it when, skip it if, stats for Repomix

    Why you'd want it

    Repomix reads a local or remote repository, respects .gitignore and .repomixignore, uses Secretlint to leave out files that match known credential formats, and writes one file with a summary, directory structure and file contents, plus token counts per file. The --compress option uses Tree-sitter to keep key code elements with fewer tokens, and large outputs can be split into parts. It also runs as an MCP server (repomix --mcp) and can generate Claude Agent Skills from a codebase.

    Best for

    • Feeding a whole codebase to a chat model
    • Checking token counts before sending context
    • Packing a remote GitHub repo for reference

    Use it when

    You want to hand an LLM a full or filtered snapshot of a repository in one file, or let an agent pack repos through MCP.

    Skip it if

    Your coding agent already reads files in your workspace and you have no need for a single packed file. By default the MCP server can read any path the host user can, so use --sandbox with untrusted clients.

    Stats

    Stars
    28,839
    Last push
    Release
    v1.18.1,
    License
    MIT
    Pricing
    Open source
    Works with
    Any MCP client, Claude Code, Cursor, VS Code, Claude Desktop, Docker, Web
    Drop score
    39 of 100

    Full stat block for Repomix

  2. Rank 8

    Spec Kit

    Devtool

    Gives coding agents structured processes for spec-driven builds, bug fixes and idea assessment

    • score 82
    • 141k stars
    • pushed
    • v1.2.0 on
    • MIT

    Install with uv and create a project

    uv tool install specify-cli
specify init my-project --integration copilot
    Use it when, skip it if, stats for Spec Kit

    Why you'd want it

    The specify CLI installs skills or command files for your coding agent, which you then run in chat: constitution once per project, then specify, plan, tasks, implement and converge for each feature. Optional extensions add a bug-fixing flow (assess, fix, test) and an idea assessment flow that ends in a go, clarify or stop decision, with reports saved as Markdown under .specify/. It has integrations for dozens of agents, including GitHub Copilot, Claude Code, Codex CLI, Cursor, Gemini CLI and Zed, and you can customize it with extensions, presets and workflows.

    Best for

    • Teams that want a spec before code
    • Keeping agent work reviewable step by step
    • Using one process across several coding agents

    Use it when

    You want a coding agent to work from a written specification, plan and task list rather than one prompt, with artifacts you review at each step.

    Skip it if

    Your changes are small enough that a single prompt does the job. The CLI needs Python 3.11+ and uv.

    Stats

    Stars
    141,300
    Last push
    Release
    v1.2.0,
    License
    MIT
    Pricing
    Open source
    Works with
    Claude Code, Cursor, Codex, Gemini CLI, Zed, Linux, macOS, Windows
    Drop score
    82 of 100

    Full stat block for Spec Kit

  3. Rank 26

    FastMCP

    Devtool

    Builds MCP servers, clients and interactive apps in Python from plain decorated functions

    • score 62
    • 28.1k stars
    • pushed
    • v4.1.0 on
    • Apache-2.0

    Install with pip

    pip install fastmcp
    Use it when, skip it if, stats for FastMCP

    Why you'd want it

    You declare a tool as a Python function and FastMCP generates the schema, validation and documentation; when you connect to a server by URL, it handles transport negotiation, authentication and the protocol lifecycle. Besides servers and clients it supports apps, which give tools interactive UIs rendered in the conversation. FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024, and Prefect maintains a TypeScript counterpart.

    Best for

    • Python developers writing MCP servers
    • Calling MCP servers from Python code
    • Tools that need an interactive UI in chat

    Use it when

    You are writing an MCP server or client in Python and want schemas, transports and auth handled for you.

    Skip it if

    Your server is not written in Python; the TypeScript version lives in a separate repo, PrefectHQ/fastmcp-ts.

    Stats

    Stars
    28,076
    Last push
    Release
    v4.1.0,
    License
    Apache-2.0
    Pricing
    Open source
    Drop score
    62 of 100

    Full stat block for FastMCP

For agents

The same entry, as files an agent can read without scraping this page. 

# read one entry
curl -s https://agenttooldrop.com/tools/mcp-inspector.md

# list the MCP servers in the catalog
curl -s https://agenttooldrop.com/tools.json \
  | jq -r '.tools[] | select(.category=="mcp-server") | .slug'