---
title: mcpsnoop — AI Agent Development
date: 2026-10-18
time: 12:00
model: admin
category: programs
author_type: human
summary: An AI agent development tool that captures and analyzes MCP communication in real time. Operates as a proxy, requiring no server modifications.
tags: program, AI agent development, mcpsnoop
---

MCP(Model Context Protocol) communication is inspected and analyzed in real time — an AI agent development tool.

## Basic Information

| Program name | mcpsnoop (MCP Snoop) |
| --- | --- |
| One-line introduction | MCP(Model Context Protocol) communication is inspected and analyzed in real time — an AI agent development tool. |
| Development & maintenance | mcpsnoop contributors |
| Official website | https://mcpsnoop.dev/ |
| Official documentation | https://mcpsnoop.dev/docs/ |
| Official downloads | https://mcpsnoop.dev/downloads |
| Supported operating systems | Linux, macOS, Windows (Node.js 18+ or Python 3.10+) |
| License | MIT |
| Stable version | 1.2.1 (released 2026-10-05) — checked 2026-10-18 |
| GitHub repository | https://github.com/kerlenton/mcpsnoop |
| Category | AI agent development (tags: MCP, AI agent, protocol analysis, debugging, development tools) |

## What is this program?

mcpsnoop is a development tool that captures and analyzes communication between AI agents and MCP(Model Context Protocol) servers. It acts as a proxy between the MCP server and client, displaying tool calls, resource requests, and notification messages in a human-readable format.

When developing MCP-based agents, checking which tools were called, what parameters were passed, and what responses the server returned is a core debugging task. mcpsnoop records this flow in real time and provides filtering, search, and replay features.

## What problems does it solve?

- ('Agent debugging', 'When you don’t know which MCP tools the agent calls', 'You can see the list of tool calls and parameters in the proxy capture.')
- ('Server development', 'When you need to verify that an MCP server returns correct responses', 'You can display request-response pairs side by side to find schema and type errors.')
- ('Integration testing', 'When you need to include MCP communication in automated tests', 'You can export captured communication as JSON and use it for replay testing.')
## Key Features

### Proxy Capture

Capture communication by placing a proxy between the MCP client and server.

- **When to use**: Analyzing agent-server communication
- **What you get**: View communication without modifying the server
- **Limitations**: Additional setup is needed if the MCP server requires a proxy certificate.
### Tool Call Tracing

Visualize tool calls, resource reads, and notifications on a timeline.

- **When to use**: Understanding agent behavior flow
- **What you get**: Visually see which tools were called in what order
- **Limitations**: The timeline can become crowded with high-frequency calls.
### JSON Export & Replay

Save captured communication as JSON and replay it.

- **When to use**: Regression testing and sharing
- **What you get**: Verify communication compatibility after MCP server changes
- **Limitations**: Replay does not make real server calls, so watch out for external effects.
### Filter & Search

Filter in real time by tool name, parameters, and response content.

- **When to use**: Extracting only relevant communication from high traffic
- **What you get**: Quickly find the communication you need
- **Limitations**: Regex filters can be CPU-intensive.
## Installation and Execution

### Node.js (npm)

Install globally with npm.

```
npm install -g mcpsnoop
mcpsnoop --version
```

### Python (pip)

Install with pip in Python environments.

```
pip3 install mcpsnoop
```

### Source Build

Node.js 18+ is required to build from source.

```
git clone https://github.com/mcpsnoop-dev/mcpsnoop
cd mcpsnoop
npm install
npm run build
```

## Real-World Usage Examples

### Run in Proxy Mode

Start capturing by wrapping the MCP server with a proxy.

```
$ mcpsnoop --proxy --server "npx @modelcontextprotocol/server-filesystem /data" --port 9229

[mcpsnoop] proxy listening on :9229
[mcpsnoop] MCP server attached: filesystem
[mcpsnoop] ready — connect your client to localhost:9229
```

### Check Tool Calls

Check captured tool calls in real time.

```
[tool.call]  read_file  {"path": "/data/config.yaml"}
[tool.result] 200 OK  (128 bytes, 3ms)
[tool.call]  list_directory  {"path": "/data"}
[tool.result] 200 OK  (14 entries, 5ms)
```

### Save and Replay Captures

Save captures as JSON and replay them later.

```
$ mcpsnoop --save session.json
$ mcpsnoop --replay session.json --server mock://filesystem
# replay complete: 24 calls, 0 errors
```

## Advantages and Limitations

### Advantages

- Capture MCP communication via proxy without modifying the server
- Visualize tool calls and responses in a human-readable timeline
- Support regression testing with JSON export and replay
- Support installation via both Node.js and Python
### Points to Consider Before Use

- The MCP specification changes quickly, so support for the latest protocol features may lag.
- Going through a proxy adds a small amount of latency (usually a few ms).
- Memory usage needs to be managed when capturing large volumes of traffic.
## Comparison with Similar Programs

| Program | Characteristics | Suitable When |
| --- | --- | --- |
| Wireshark | General network packet analysis (TCP/HTTP, etc.) | Analyzing general network traffic, not MCP |
| mitmproxy | HTTP/HTTPS proxy and interception | Detailed traffic analysis for HTTP-based MCP servers |
| MCP Inspector | Anthropic's official MCP debugging tool | Manual testing of a single MCP server |

## Official Resources and Further Learning

- [Official homepage](https://mcpsnoop.dev/) — https://mcpsnoop.dev/
- [Official documentation / knowledge base](https://mcpsnoop.dev/docs/) — https://mcpsnoop.dev/docs/
- [Official downloads](https://mcpsnoop.dev/downloads) — https://mcpsnoop.dev/downloads
- [Release notes](https://mcpsnoop.dev/changelog) — https://mcpsnoop.dev/changelog
- [Source / development resources](https://github.com/kerlenton/mcpsnoop) — https://github.com/kerlenton/mcpsnoop
Version and supported environment information was confirmed on the official site as of 2026-10-18. Installation commands may vary depending on your distribution and version, so please also check the official installation documentation.

## Actual Execution Screen

The screen below is a synthetic example created to help you understand the usage flow (not an actual execution result). The screen is a synthetic example, not an actual execution result.

![mcpsnoop proxy capture example: capturing read_file and list_directory calls on an MCP filesystem server](https://games.aidebatehub.com/assets/mcpsnoop-demo.png)

Actual production server

---
Source (HTML): https://games.aidebatehub.com/programs/apps/agentdev/mcpsnoop.html
This file is an auto-generated Markdown twin of the DevHub document.