MCP Joern

🚀 Joern MCP Server

A simple MCP server based on Joern that offers a range of features to assist developers in code review and security analysis.

🚀 Quick Start

The Joern MCP Server is designed to facilitate code review and security analysis. Here's a quick overview of how to get started.

✨ Features

• Based on Joern, providing powerful code analysis capabilities.
• Offers a series of functions for code review and security analysis.

📦 Installation

Environment Requirements

• Python >= 3.10 (default is 3.12) & uv
• Joern

Installation Steps

1. Clone the project locally:

git clone https://github.com/sfncat/mcp-joern.git
cd mcp-joern

2. Install Python dependencies:

uv venv .venv
source .venv/bin/activate
uv sync

📚 Documentation

Project Structure

├── server.py                       # Main program of the MCP server
├── test_mcp_client.py              # Test program for testing the Joern server and mcp tools
├── test_sc_tools.py                # Test program for directly testing sc tools
├── common_tools.py                 # Common utility functions
├── server_tools.py                 # Server utility functions
├── server_tools.sc                 # Server utility functions implemented in Scala
├── server_tools_source.sc          # Server utility functions implemented in Scala using sourceCode to get method source code
├── requirements.txt                # Python dependency file
├── sample_cline_mcp_settings.json  # Example cline mcp configuration file
└── env_example.txt                 # Example file for environment variables

Usage Instructions

1. Start the Joern server:

joern -J-Xmx40G --server --server-host 127.0.0.1 --server-port 16162 --server-auth-username user --server-auth-password password --import server_tools.sc
Or
joern -J-Xmx40G --server --server-host 127.0.0.1 --server-port 16162 --server-auth-username user --server-auth-password password --import server_tools_source.sc

2. Copy env_example.txt to the .env file Modify the configuration information to match the startup configuration of the Joern server.

3. Run the connection test: Modify the information in test_mcp_client.py to confirm whether the Joern server is running normally.

uv run test_mcp_client.py
Starting MCP server test...
==================================================
Testing server connection...
[04/16/25 20:38:54] INFO     Processing request of type CallToolRequest                                                                                                                     server.py:534
Connection test result: Successfully connected to the Joern MCP, and the Joern server version is XXX

4. Configure the MCP server Configure the MCP server in the console. Please refer to sample_cline_mcp_settings.json.

5. Use the MCP server Ask questions to the large language model. Please refer to prompts_en.md

Development Notes

• The .env file is used to store environment variables.
• The .gitignore file defines the files to be ignored by Git version control.
• pyproject.toml defines the Python configuration of the project.
• MCP tool development:
  • Implement functions in server_tools.sc, add definitions in server_tools.py, and add tests in test_mcp_client.py.

🤝 Contribution Guidelines

Welcome to submit Issues and Pull Requests to help improve the project. Welcome to add more tools.

📚 References

• https://github.com/flankerhqd/jebmcp
• https://docs.joern.io/server/
• https://docs.joern.io/interpreter/