dnSpy MCP Extension

A Model Context Protocol (MCP) extension for dnSpyEx that exposes .NET assembly analysis tools to AI assistants like Claude.

Features

MCP Tools (10 total)

The extension provides 10 powerful tools for analyzing .NET assemblies:

1. list_assemblies - List all loaded assemblies with metadata
2. get_assembly_info - Get detailed information about a specific assembly
3. list_types - List all types in an assembly with filtering options
4. get_type_info - Get comprehensive type information (fields, properties, methods, events)
5. get_type_fields - Filter fields by wildcard pattern (e.g., *Bonus*)
6. get_type_property - Get detailed property information including getters/setters
7. find_path_to_type - Find property/field chains connecting two types (BFS algorithm)
8. get_method_signature - Get detailed method signature information
9. decompile_method - Decompile method to C# source code
10. search_types - Search for types by name pattern across all assemblies

MCP Resources (6 total)

Comprehensive embedded BepInEx plugin development documentation:

1. plugin-structure - Basic plugin setup and metadata
2. harmony-patching - HarmonyX patching guide (Prefix/Postfix/Transpiler)
3. configuration - Configuration system usage
4. common-scenarios - 8 common plugin development patterns
5. il2cpp-guide - Complete IL2CPP development guide
6. mono-vs-il2cpp - Side-by-side comparison and migration guide

All documentation is self-contained within the extension DLL - no internet connection required.

Installation

From Release (Recommended)

1. Download the latest release from the Releases page
2. Choose the appropriate DLL for your dnSpy version:
   • dnSpy.Extension.MCP-net48.dll - For dnSpy .NET Framework 4.8
   • dnSpy.Extension.MCP-net8.0.dll - For dnSpy .NET 8.0
3. Rename the file to dnSpy.Extension.MCP.x.dll
4. Copy to <dnSpy-Install-Path>\bin\Extensions\dnSpy.Extension.MCP\
5. Restart dnSpy

From Source

# Clone dnSpyEx repository
git clone https://github.com/dnSpyEx/dnSpy.git
cd dnSpy

# Clone this extension into Extensions folder
cd Extensions
git clone https://github.com/KernelErr/dnSpy.Extension.MCP.git

# Build the extension
cd dnSpy.Extension.MCP
dotnet build -c Release

# Copy to dnSpy installation
copy bin\Release\net48\dnSpy.Extension.MCP.x.dll <dnSpy-Install-Path>\bin\Extensions\dnSpy.Extension.MCP\

Configuration

Access settings in dnSpy: Edit → Settings → MCP Server

Available settings:

• Enable Server - Start/stop the MCP server
• Port - HTTP server port (default: 3000)
• Host - Bind address (default: localhost for .NET Framework)

Usage

With Claude Desktop

Add to your Claude Desktop configuration (claude_desktop_config.json):

{
  "mcpServers": {
    "dnspy": {
      "command": "http",
      "args": ["http://localhost:3000"]
    }
  }
}

Testing the Server

Check server health:

curl http://localhost:3000/health

Expected response:

{"status":"ok","service":"dnSpy MCP Server"}

Development

Building

# Build for .NET Framework 4.8
dotnet build -c Release -f net48

# Build for .NET 8.0
dotnet build -c Release -f net8.0-windows

Project Structure

dnSpy.Extension.MCP/
├── .github/workflows/      # GitHub Actions (build, release)
├── McpServer.cs           # HTTP server (Kestrel/.NET, HttpListener/.NET Framework)
├── McpProtocol.cs         # JSON-RPC 2.0 protocol models
├── McpTools.cs            # 10 MCP tools implementation
├── McpSettings.cs         # Settings UI and persistence
├── BepInExResources.cs    # Embedded documentation (6 resources)
└── dnSpy.Extension.MCP.csproj

Architecture

• Multi-framework support: Targets both net48 and net8.0-windows
• Server implementation:
  • .NET 8.0: ASP.NET Core Kestrel (high performance)
  • .NET Framework: HttpListener (compatibility)
• MEF integration: Uses dnSpy's Managed Extensibility Framework
• Protocol: JSON-RPC 2.0 over HTTP
• CORS enabled: Allows cross-origin requests

Protocol

The extension implements Model Context Protocol (MCP) specification version 2024-11-05.

Supported methods:

• initialize - Server initialization
• ping - Keepalive
• tools/list - List available tools
• tools/call - Execute a tool
• resources/list - List documentation resources
• resources/read - Read documentation content
• notifications/* - Handle client notifications

CI/CD

GitHub Actions Workflows

1. Build Workflow (.github/workflows/build.yml)

   • Triggers: Push to master/main, Pull Requests
   • Builds both net48 and net8.0-windows
   • Runs on Debug and Release configurations
   • Uploads artifacts for Release builds

2. Release Workflow (.github/workflows/release.yml)

   • Triggers: Push tags (v*.*.*) or manual dispatch
   • Builds release DLLs
   • Creates GitHub release with assets
   • Auto-generates release notes

Creating a Release

# Tag the release
git tag v1.0.0
git push origin v1.0.0

# GitHub Actions will automatically:
# 1. Build both net48 and net8.0 DLLs
# 2. Create a GitHub release
# 3. Upload DLLs and README as assets

Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

GitHub Actions will automatically build and test your PR.

Technical Details

Dependencies

• dnSpy.Contracts.DnSpy - dnSpy API contracts
• dnSpy.Contracts.Logic - Core logic contracts
• dnlib - .NET metadata library
• System.Text.Json - JSON serialization
• ASP.NET Core (net8.0 only) - Kestrel HTTP server

BFS Path Finding

The find_path_to_type tool uses breadth-first search to find navigation paths between types:

// Example: Find path from PlayerController to HealthBonus
// Result: PlayerController -> PlayerState -> Bonuses -> HealthBonus

Decompilation

Uses dnSpy's built-in decompiler with configurable options:

• Language: C#
• Indentation: Tabs
• Comment verbosity: Configurable

License

This extension follows the same license as dnSpyEx. Please see the dnSpyEx repository for license information.

Acknowledgments

• dnSpyEx - The .NET debugger and assembly editor (continuation of dnSpy)
• Model Context Protocol - Anthropic's MCP specification
• BepInEx - Unity game modding framework

Troubleshooting

Extension not loading

• Check dnSpy console for error messages
• Verify DLL is in correct location
• Ensure file is named dnSpy.Extension.MCP.x.dll

Server not starting

• Check port is not already in use
• Review dnSpy console logs
• Try changing port in settings

Build errors

• Ensure dnSpy repository is cloned in parent directory
• Run dotnet restore in dnSpy root
• Check .NET SDK version (requires .NET 8.0 SDK)

Support

For issues, questions, or feature requests, please open an issue on the GitHub repository.