Mcpsnoop Review 2026: Wireshark for MCP, in Your Terminal

If you’ve ever wondered “why didn’t my agent call that tool?” or “what arguments did it actually send?”, the official MCP Inspector can’t tell you — it connects as a second client off to the side. Mcpsnoop sits in the real data path instead, and that single design choice is why it’s being called “Wireshark for MCP.”

What Mcpsnoop Does

Mcpsnoop is a transparent proxy plus a live terminal UI. You wrap your MCP server command with it (mcpsnoop -- node build/index.js), and it forwards every byte verbatim while copying each JSON-RPC frame to a k9s-style TUI. You immediately see every tool call, argument, response, and stderr line as your real client (Cursor, Claude Code, Codex) and server actually talk.

Use Cases

• Debugging silent failures — a tool that should have been called but wasn’t, or was called with wrong args.
• Tracing hangs — flag pending calls that never resolve.
• Auditing what your agent really does — every frame, captured, with full-text search and column sorting.
• CI checks — mcpsnoop check can validate MCP traffic in pipelines.

Key Features

In-Path, Not Side-Client

The official Inspector watches from the sidelines. Mcpsnoop is in the pipe, so it sees exactly what both sides say — regardless of what language the server is written in.

Live TUI

A bubbletea-powered terminal UI: filter by tool, method, status, or direction; search frames; pause and follow; sort by column. Press / to filter, r to replay a call, e to export.

Detects the Ugly Stuff

Slow calls, hung calls, and malformed JSON-RPC frames are flagged automatically — the exact failures that are painful to find in raw logs.

Replay & Export

Re-run a captured call against a fresh server instance for fast iteration. Export any session as JSON, self-contained HTML, plain text, or OTLP.

Single Binary, MIT

Written in Go with no runtime dependencies. Install via go install, Homebrew, or grab a prebuilt binary for any platform (latest: v0.8.0, Jul 2026).

How It Compares

Tool	Sees real traffic	Live TUI	Zero-config	Replay	Export
Mcpsnoop	✅	✅	✅	✅	✅
MCP Inspector	❌ (side client)	❌	partial	❌	❌
mitmproxy	✅ (HTTP only)	❌	no	❌	partial

The Verdict

Mcpsnoop is the debugging tool MCP should have shipped with. It’s free, open source (MIT), and solves a real pain point for anyone building MCP servers or wiring agents to tools. The only caveat: it’s a terminal tool for developers, not a GUI — but if you live in Cursor or Claude Code, that’s exactly where you want it.