MCPSnoop Review 2026 — Wireshark for MCP: Debug Every Tool Call

Overview

MCPSnoop calls itself “Wireshark for MCP” — and it lives up to the name. Released on June 27, 2026, this open-source Go tool has already racked up 179 GitHub stars. It solves a genuine pain point in the MCP ecosystem: when your AI client calls an MCP server, what actually happens?

The official MCP Inspector works as a separate client — it never sees the actual traffic between your client and your server. MCPSnoop sits directly in the pipe, acting as a transparent proxy that copies every JSON-RPC frame to a live terminal UI.

How It Works

MCPSnoop runs as two roles in one binary:

1. The shim (mcpsnoop -- <server-command>) — A transparent wrapper your AI client spawns. It forwards bytes verbatim between client and server while shipping a copy of each frame to the hub.
2. The hub/TUI (mcpsnoop with no arguments) — The live terminal interface that displays all captured traffic.

The two roles auto-discover each other through a well-known socket and on-disk logs. There’s no startup order to remember — open the TUI before or after your client, it doesn’t matter.

Hands-On Testing

Setting up MCPSnoop is refreshingly simple. For a stdio-based MCP server, you modify your AI client’s MCP config to wrap the server command:

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

Everything after -- is your normal server command. For streamable HTTP servers, MCPSnoop also works as a reverse proxy:

mcpsnoop http --target http://localhost:3000/mcp --listen :7000

Once running, every tool call appears in the TUI with:

• Color-coded requests and responses
• Error and slow-call flags
• Live timers on in-flight (“PENDING”) requests
• Tool-level result.isError indicators

Replay Capability

One standout feature: press r in the TUI to replay any captured tool call against a fresh, isolated copy of the server. This is the fastest feedback loop for iterating on MCP server tool implementations.

Filtering

Press / to filter the stream. Combine space-separated tokens:

• tool:search status:slow — slow calls to a search tool
• dir:s2c kind:req — server-initiated requests (sampling, roots)
• Plain text matches method, tool name, ID, and payload

Capability Inspector

Press c to see exactly what the client and server agreed on at the handshake. This alone is worth the install — capability negotiation has been a black box until now.

Comparison: MCPSnoop vs Alternatives

Feature	MCP Inspector	mcp-trace	MCPSnoop
Sees your real client↔server traffic	❌	✅	✅
Interactive terminal UI	❌	✅	✅
Zero-config, no flags or ordering	❌	❌	✅
Capability inspector	Partial	❌	✅
Replay a captured call	❌	❌	✅
Single binary, no runtime deps	❌	Varies	✅

Community Reception

The developer community has embraced MCPSnoop quickly. On Hacker News it was noted as “the debugging tool MCP has been missing” — a sentiment echoed by several MCP server maintainers on GitHub. The ability to see actual tool-calling traffic without setup friction has been the most praised feature.

The project is actively maintained with daily commits (last updated July 4, 2026) and clear contribution guidelines.

Who Should Use MCPSnoop

MCP server developers get the most immediate value — debugging why a tool call fails, inspecting arguments, and replaying calls in isolation. It’s also invaluable for:

• AI agent builders integrating multiple MCP tools
• Platform engineers debugging capability negotiation
• Anyone troubleshooting silent MCP failures where a tool “just isn’t called”

Verdict

MCPSnoop fills a genuine gap in the MCP tooling ecosystem. The MCP Inspector exists, but it’s a second-class citizen that never touches the real data path. MCPSnoop sits where it matters — in the actual pipe between your client and server.

At 179 GitHub stars and growing rapidly, it’s already proven its value. The zero-config approach, replay capability, and clean TUI make it the best MCP debugging tool available today.

Rating: 8.6/10 — Essential for anyone building with MCP.

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Tested with Claude Desktop, Claude Code, and Cursor against custom MCP servers. MCPSnoop is MIT-licensed and available at github.com/kerlenton/mcpsnoop.