What is Mcp Joern

mcp-joern is a simple MCP Server based on Joern, designed to assist developers in code review and security analysis.

Use cases

Use cases for mcp-joern include automated code reviews, security vulnerability assessments, and educational purposes for understanding code structure and security.

How to use

To use mcp-joern, clone the project from GitHub, install the required Python dependencies, start the Joern server, configure the MCP server, and run the demo script to test the connection.

Key features

Key features include integration with Joern for code analysis, a simple setup process, and the ability to interact with a large language model for querying code-related questions.

Where to use

mcp-joern can be used in software development environments, particularly in code review processes and security analysis tasks.

Joern MCP Server

A simple MCP Server for Joern.

Project Introduction

This project is an MCP Server based on Joern, providing a series of features to help developers with code review and security analysis.

Environment Requirements

• Python >= 3.10 (default 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
   

Project Structure

├── server.py                       # MCP Server main program
├── test_mcp_client.py              # Test program for joern server and mcp tool
├── test_sc_tools.py                # Direct test program for sc tools
├── common_tools.py                 # Common utility functions
├── server_tools.py                 # Server utility functions
├── server_tools.sc                 # Scala implementation of server utility functions
├── server_tools_source.sc          # Scala implementation of server utility functions,use sourceCode to get the source code of method
├── requirements.txt                # Python dependency file
├── sample_cline_mcp_settings.json  # Sample cline mcp configuration file
└── env_example.txt                 # Environment variables example file

Usage

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 .env
   Modify the configuration information to match the joern server startup configuration

3. Run the test connection:
   Modify the information in test_mcp_client.py to confirm the joern server is working properly

   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 Joern MCP, joern server version is XXX
   

4. Configure MCP server
   Configure the mcp server in cline, refer to sample_cline_mcp_settings.json.

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

Development Notes

• .env file is used to store environment variables
• .gitignore file defines files to be ignored by Git version control
• pyproject.toml defines the Python configuration for the project
• MCP tool development
  • Implement 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/