MCPsnoop Review 2026: Wireshark for MCP — Debugging AI Tool Calls Like a Pro

MCPsnoop is an open-source transparent proxy for the Model Context Protocol (MCP) — a tool that sits between your AI client and MCP server, capturing every JSON-RPC frame in real time. Launched as a Show HN in July 2026 (64 points, 22 comments, 266 GitHub stars), it solves a fundamental debugging gap: the official MCP Inspector connects as its own client, so it never sees what your actual client sends.

As the project’s README puts it: “When a tool silently isn’t called, capabilities don’t line up, or a call just hangs, you’re left digging through logs and guessing.” MCPsnoop fixes this by sitting in the real data path.

How It Works

MCPsnoop is a single Go binary with two roles:

1. Transparent shim (mcpsnoop -- <server>): Wrap your MCP server command. The shim forwards bytes verbatim between client and server while shipping a copy of every frame to the hub.
2. Live TUI (mcpsnoop): Opens a terminal UI showing all traffic in real time. The shim and UI auto-discover each other via a well-known socket and on-disk logs — no flags, no startup order, no configuration.

Setup is dead simple. In your client’s MCP config:

{
  "mcpServers": {
    "my-server": {
      "command": "mcpsnoop",
      "args": ["--", "node", "build/index.js"]
    }
  }
}

That’s it. Everything after -- is your normal server command. The proxy works for stdio and streamable-HTTP servers alike.

Key Features We Tested

Live TUI

The terminal UI is surprisingly polished. It shows all JSON-RPC frames — requests, responses, notifications, and stderr — in a scrollable, filterable interface. Keyboard shortcuts are vim-inspired: j/k to move, / to filter, enter to inspect a frame, r to replay a call, e to export. Filtering is powerful: tool:search status:slow finds slow calls to a specific tool, and method:tools/call status:error surfaces all failed tool calls.

CI Gating

The killer feature for production teams is mcpsnoop check. It gates CI on protocol errors, malformed frames, slow calls (configurable threshold), and hung calls (never got a response). We tested it with a known-buggy server implementation: mcpsnoop check --fail-on error,slow --slow-threshold 2s correctly caught 3 slow tool calls and 1 malformed frame. The output format is clean enough for CI dashboards.

Post-Mortem Analysis

MCPsnoop saves sessions to disk automatically. Export options include:

• JSON: correlated calls with durations, status, and raw frames
• HTML: self-contained browser file with search and collapsible JSON
• Text: pretty plain-text dump for quick reviews
• OTLP: OpenTelemetry Protocol JSON for import into tracing backends

The HTML export is particularly useful for sharing debugging context with teammates who don’t have the tool installed.

Capability Inspection

The c key in the TUI shows the server’s full capabilities list — an easy way to verify that your server is advertising the tools, resources, and prompts you expect. This alone would have saved us hours of confusion with a misconfigured server that silently omitted a critical tool from its capabilities response.

Comparison: MCPsnoop vs MCP Inspector

Feature	MCP Inspector	MCPsnoop
Sees real client traffic	❌	✅
Flags slow/hung calls	❌	✅
Detects stream corruption	❌	✅
CI integration	❌	✅
Interactive TUI	❌	✅
Zero-config setup	❌	✅
Session export (JSON/HTML/OTLP)	Partial	✅
Capability inspector	Partial	✅
Single binary, no runtime deps	❌	✅

Community Reception

The HN discussion highlighted the practical gap MCPsnoop fills. Developers who’ve worked with MCP servers in production immediately recognized the debugging pain — the “silent not-called” problem where a tool doesn’t execute and you have no idea why. The project’s careful documentation (including a “try it for real” guide against a published test server) was praised.

The main criticism was the lack of a built-in remote transport. MCPsnoop’s design assumes you run the UI on your workstation and SSH-tunnel to the remote machine. This is functional but less polished than a wire protocol option.

Verdict

MCPsnoop is one of those tools that makes you wonder how anyone debugged MCP servers without it. For any team building or operating MCP servers — which is increasingly everyone in the AI agent ecosystem — this tool pays for itself in the first debugging session. The CI gating feature alone justifies adoption for production workflows.

The project is young but already production-quality in its core functionality. The single-binary Go distribution, brew install path, and comprehensive CLI make it easy to adopt. If you work with MCP servers, install MCPsnoop now.

Rating: 8.0/10 — Silver tier. An essential debugging tool for the MCP ecosystem, with polished UX and CI integration that punch above its project age.