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MCP Tap

v1.0.0•Developer Tools•stable

mcp-tap is like wireshark but for MCP

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What is MCP Tap?

MCP Tap is a Model Context Protocol (MCP) server that allows AI assistants like Claude, Cursor, and VS Code to mcp-tap is like wireshark but for mcp

mcp-tap is like wireshark but for MCP

This server falls under the Developer Tools category on MCPgee, the world's largest MCP server directory with 33,000+ servers.

Features

  • mcp-tap is like wireshark but for MCP

Use Cases

Debug MCP protocol interactions
Monitor tool calls and responses
jondot

Maintainer

LicenseMIT
Languagerust
Versionv1.0.0
UpdatedMar 22, 2026
Statushealthy
Maintenanceactive

Works with

ClaudeOpenAIwindowsmacoslinux
View SourceBrowse All Servers

Installation

Manual Installation

npx mcptap

Configuration

Configuration Details

Config File

claude_desktop_config.json

Performance

Response Metrics

Response Time< 200ms
ThroughputMedium

Resource Usage

Memory UsageLow
CPU UsageLow

How to Set Up and Use MCP Tap

mcp-tap is a Wireshark-like traffic inspector for the Model Context Protocol, written in Rust. It works by acting as a transparent proxy between your MCP client and your MCP servers — rewriting your MCP configuration to route traffic through itself, displaying syntax-highlighted JSON of every tool call and response in real time, and restoring the original configuration when you are done. Developers use it to debug misbehaving MCP servers, understand what an AI client is actually sending, enforce policy rules via CEL expressions to allow or block specific tool calls, and analyze traffic patterns across both stdio and HTTP transports.

Prerequisites

  • A pre-compiled mcp-tap binary for your platform (download from https://github.com/jondot/mcptap/releases)
  • An existing MCP configuration file (e.g. ~/.config/mcp.json) with at least one MCP server configured
  • MCP-compatible client such as Claude Desktop or Cursor already set up
  • Optional: a YAML policy file with CEL expressions for filtering or blocking specific traffic
1

Download the mcp-tap binary

Go to the GitHub Releases page and download the pre-compiled binary for your operating system (macOS, Linux, or Windows). Place it in a directory on your PATH.

# Example for macOS ARM64:
curl -L https://github.com/jondot/mcptap/releases/latest/download/mcptap-aarch64-apple-darwin.tar.gz | tar xz
mv mcptap /usr/local/bin/
mcptap --version
2

Start monitoring MCP traffic

Run mcp-tap tap pointing at your MCP configuration file. The tool rewrites the config to insert itself as a proxy, backs up the original, and begins displaying live traffic in your terminal. Your MCP client continues working normally.

mcp-tap tap --mcp-config ~/.config/mcp.json
3

Apply a policy file to filter or block traffic

Create a YAML policy file with CEL expressions that match specific tool names, methods, or argument patterns. Use --mode observe to highlight matching traffic or --mode enforce to block matching requests.

# policy.yaml example:
rules:
  - name: "block dangerous tool"
    match: 'tool_name == "execute_shell_command"'
    action: block

mcp-tap tap --mcp-config ~/.config/mcp.json --policy policy.yaml --mode enforce
4

Output traffic to stdout for scripting

Pipe the raw MCP traffic to other tools for analysis or logging by adding the --stdout flag, which disables the interactive TUI and writes JSON lines to standard output.

mcp-tap tap --mcp-config ~/.config/mcp.json --stdout | jq '.method'
5

Restore your original MCP configuration

When you are done debugging, run the untap command to restore the original MCP configuration that mcp-tap backed up. This removes the proxy from the traffic path.

mcp-tap untap --mcp-config ~/.config/mcp.json

MCP Tap Examples

Client configuration

mcp-tap does not need a separate MCP client config entry — it rewrites your existing MCP config to proxy through itself. Your existing Claude Desktop config remains unchanged in terms of servers listed; mcp-tap inserts itself transparently.

{
  "mcpServers": {
    "your-existing-server": {
      "command": "node",
      "args": ["/path/to/your-mcp-server/index.js"]
    }
  }
}

Prompts to try

mcp-tap is a developer debugging tool rather than a conversational AI tool. These are terminal commands and investigation scenarios rather than AI chat prompts.

- Run: mcp-tap tap --mcp-config ~/.config/mcp.json  (to start live monitoring)
- Run: mcp-tap tap --mcp-config ~/.config/mcp.json --stdout | jq '.params.name'  (extract tool names)
- Run: mcp-tap untap --mcp-config ~/.config/mcp.json  (restore config when done)
- Ask your AI: "Call the list_files tool" and watch mcp-tap capture the exact JSON exchanged

Troubleshooting MCP Tap

MCP client stops working after running mcp-tap

If mcp-tap exited unexpectedly without running untap, your MCP config may still be pointing at the proxy. Run mcp-tap untap --mcp-config ~/.config/mcp.json to restore the original configuration. A backup is stored alongside the config file.

mcp-tap shows no traffic even though the AI client is calling tools

Confirm mcp-tap rewrote the correct config file. Different MCP clients use different config paths — Claude Desktop uses ~/Library/Application Support/Claude/claude_desktop_config.json on macOS, while Cursor uses .cursor/mcp.json. Point --mcp-config at the file your specific client reads.

Policy file CEL expressions are not matching expected traffic

Use --mode observe first before --mode enforce to see which traffic is being highlighted. Check the CEL expression syntax carefully — string comparisons are case-sensitive and field names must match the exact MCP protocol field names (tool_name, method, params, etc.).

Frequently Asked Questions about MCP Tap

What is MCP Tap?

MCP Tap is a Model Context Protocol (MCP) server that mcp-tap is like wireshark but for mcp It connects AI assistants to external tools and data sources through a standardized interface.

How do I install MCP Tap?

Follow the installation instructions on the MCP Tap GitHub repository. Clone the repo, install dependencies, and add the server config to your AI client.

Which AI clients work with MCP Tap?

MCP Tap works with all major MCP-compatible AI clients including Claude Desktop, Claude Code, Cursor, VS Code (GitHub Copilot), Windsurf, and Cline.

Is MCP Tap free to use?

Yes, MCP Tap is open source and available under the MIT license. You can use it freely in both personal and commercial projects.

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Quick Config Preview

{ "mcpServers": { "mcptap": { "command": "npx", "args": ["-y", "mcptap"] } } }

Add this to your claude_desktop_config.json or .cursor/mcp.json

Read the full setup guide →

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