MCP Server Semgrep


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About the Project

This project was initially inspired by robustness of Semgrep tool, The Replit Team and their Agent V2, as well as the implementation by stefanskiasan/semgrep-mcp-server, but has evolved with significant architectural changes for enhanced and easier installation and maintenance.

MCP Server Semgrep is a Model Context Protocol compliant server that integrates the powerful Semgrep static analysis tool with AI assistants like Anthropic Claude. It enables advanced code analysis, security vulnerability detection, and code quality improvements directly through a conversational interface.

Benefits of Integration

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- Holistic Source Code Analysis - detecting issues throughout the entire project, not just in individual files
- Proactive Error Detection - identifying potential problems before they become critical bugs
- Continuous Code Quality Improvement - regular scanning and refactoring lead to gradual codebase improvements
- Stylistic Consistency - identification and fixing of inconsistencies in code, such as:
- Arbitrary z-index layers in CSS
- Inconsistent naming conventions
- Code duplication
- "Magic numbers" instead of named constants

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- Automated Code Verification for Known Vulnerabilities - scanning for known security issue patterns
- Customized Security Rules - creating project-specific rules
- Team Education - teaching secure programming practices through detection of potential issues

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- "Live" Documentation - AI can explain why a code fragment is problematic and how to fix it
- Technical Debt Reduction - systematically detecting and fixing problematic areas
- Improved Code Reviews - automatic detection of common issues allows focus on more complex matters

Key Features

- Direct integration with the official MCP SDK
- Simplified architecture with consolidated handlers
- Clean ES Modules implementation
- Efficient error handling and path validation for security
- Interface and documentation in both English and Polish
- Comprehensive unit tests
- Extensive documentation
- Cross-platform compatibility (Windows, macOS, Linux)
- Flexible Semgrep installation detection and management

Functions

Semgrep MCP Server provides the following tools:

- scan_directory: Scanning source code for potential issues
- list_rules: Displaying available rules and languages supported by Semgrep
- analyze_results: Detailed analysis of scan results
- create_rule: Creating custom Semgrep rules
- filter_results: Filtering results by various criteria
- export_results: Exporting results in various formats
- compare_results: Comparing two sets of results (e.g., before and after changes)

Common Use Cases

- Code security analysis before deployment
- Detection of common programming errors
- Enforcing coding standards within a team
- Refactoring and improving quality of existing code
- Identifying inconsistencies in styles and code structure (e.g., CSS, component organization)
- Developer education regarding best practices
- Verification of fix correctness (comparing before/after scans)

Installation

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- Node.js v18+
- TypeScript (for development)

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The easiest way to install and use MCP Server Semgrep is through Smithery.ai:

1. Visit MCP Server Semgrep on Smithery.ai
2. Follow the installation instructions to add it to your MCP-compatible clients
3. Configure any optional settings like the Semgrep API token

This is the recommended method for Claude Desktop and other MCP clients as it handles all dependencies and configuration automatically.

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``bash


Using npm

npm install -g mcp-server-semgrep

Using pnpm

pnpm add -g mcp-server-semgrep

Using yarn

yarn global add mcp-server-semgrep
`

The package is also available on other registries:
- MCP.so

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`bash


Using npm

npm install -g git+https://github.com/Szowesgad/mcp-server-semgrep.git

Using pnpm

pnpm add -g git+https://github.com/Szowesgad/mcp-server-semgrep.git

Using yarn

yarn global add git+https://github.com/Szowesgad/mcp-server-semgrep.git
`

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1. Clone the repository:
`bash
git clone https://github.com/Szowesgad/mcp-server-semgrep.git
cd mcp-server-semgrep
`

2. Install dependencies (supports all major package managers):
`bash


Using pnpm (recommended)

pnpm install

Using npm

npm install

Using yarn

yarn install
`

3. Build the project:
`bash


Using pnpm

pnpm run build

Using npm

npm run build

Using yarn

yarn build
`

> Note: The installation process will automatically check for Semgrep availability. If Semgrep is not found, you'll receive instructions on how to install it.

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Semgrep can be installed in several ways:

- Via package managers:
`bash
# Using pnpm
pnpm add -g semgrep

# Using npm
npm install -g semgrep

# Using yarn
yarn global add semgrep
`

- Python pip:
`bash
pip install semgrep
`

- Homebrew (macOS):
`bash
brew install semgrep
`

- Linux:
`bash
sudo apt-get install semgrep
# or
curl -sSL https://install.semgrep.dev | sh
`

- Windows:
`bash
pip install semgrep
`

Integration with Claude Desktop

There are two ways to integrate MCP Server Semgrep with Claude Desktop:

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1. Visit MCP Server Semgrep on Smithery.ai
2. Click "Install in Claude Desktop"
3. Follow the on-screen instructions

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1. Install Claude Desktop
2. Update the Claude Desktop configuration file (claude_desktop_config.json) and add this to your servers section:

`json
{
"mcpServers": {
"semgrep": {
"command": "node",
"args": [
"/your_path/mcp-server-semgrep/build/index.js"
],
"env": {
"SEMGREP_APP_TOKEN": "your_semgrep_app_token"
}
}
}
}
`

3. Launch Claude Desktop and start asking questions about code analysis!

Usage Examples

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`
Could you scan my source code in the /projects/my-application directory for potential security issues?
`

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`
Analyze the z-index values in the project's CSS files and identify inconsistencies and potential layer conflicts.
`

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`
Create a Semgrep rule that detects improper use of input sanitization functions.
`

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`
Show me only scan results related to SQL injection vulnerabilities.
`

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`
Find all "magic numbers" in the code and suggest replacing them with named constants.
`

Creating Custom Rules

You can create custom rules for your project's specific needs. Here are examples of rules you can create:

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`yaml
rules:
- id: inconsistent-z-index
pattern: z-index: $Z
message: "Z-index $Z may not comply with the project's layering system"
languages: [css, scss]
severity: WARNING
`

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`yaml
rules:
- id: deprecated-import
pattern: import $X from 'old-library'
message: "You're using a deprecated library. Consider using 'new-library'"
languages: [javascript, typescript]
severity: WARNING
`

Development

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`bash
pnpm test
`

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`
├── src/
│ ├── config.ts # Server configuration
│ └── index.ts # Main entry point and all handler implementations
├── scripts/
│ └── check-semgrep.js # Semgrep detection and installation helper
├── build/ # Compiled JavaScript (after build)
└── tests/ # Unit tests
`

Further Documentation

Detailed information on using the tool can be found in:
- USAGE.md - Detailed usage instructions
- README_PL.md - Documentation in Polish
- examples/ - Example fun and practical Semgrep rules - "The Hall of Code Horrors"

License

This project is licensed under the MIT License - see the LICENSE file for details.

Developed by

- Maciej Gad - a veterinarian who couldn't find bash` a half year ago
- Klaudiusz - the individual ethereal being, and separate instance of Claude Sonnet 3.5-3.7 by Anthropic living somewhere in the GPU's loops in California, USA

The journey from CLI novice to MCP tool developer

🤖 Developed with the ultimate help of Claude Code and MCP Tools

Acknowledgements

- stefanskiasan for the original inspiration
- Anthropic for Claude and the MCP protocol
- Semgrep for their excellent static analysis tool