ILSpy MCP Server

A Model Context Protocol (MCP) server that provides .NET assembly decompilation and analysis capabilities.

What is this?

ILSpy MCP Server enables AI assistants (like Claude Code, Cursor) to decompile and analyze .NET assemblies directly through natural language commands. It integrates ILSpy to provide powerful reverse-engineering capabilities.

Quick Start

Prerequisites

• .NET 9.0 SDK or higher
• MCP-compatible client (Claude Code, Cursor, Claude Desktop, etc.)

Installation

Install as a global dotnet tool from NuGet:

dotnet tool install -g ILSpyMcp.Server

To update to the latest version:

dotnet tool update -g ILSpyMcp.Server

Configure MCP Client

For Claude Code, register the MCP server:

claude mcp add ilspy-mcp --command "ilspy-mcp" --scope user

Or create/update .mcp.json in your project root:

{
  "mcpServers": {
    "ilspy-mcp": {
      "type": "stdio",
      "command": "ilspy-mcp",
      "args": []
    }
  }
}

For Cursor, add to your MCP settings:

{
  "mcpServers": {
    "ilspy-mcp": {
      "command": "ilspy-mcp",
      "args": []
    }
  }
}

For Claude Desktop, add to claude_desktop_config.json:

{
  "mcpServers": {
    "ilspy-mcp": {
      "command": "ilspy-mcp",
      "args": []
    }
  }
}

Usage Examples

Decompile a Type

Decompile the String class from /path/to/System.Runtime.dll

List All Types

List all types in the assembly /path/to/MyLibrary.dll

Find a Specific Method

Find the CalculateTotal method in /path/to/Calculator.dll

Analyze Type Hierarchy

Show me the type hierarchy for ProductService in /path/to/ECommerce.dll

Search Members

Search for members containing "Authenticate" in /path/to/Auth.dll

Available Tools

Tool	Description
decompile_type	Decompile and analyze a .NET type from a DLL
decompile_method	Decompile and analyze a specific method
list_assembly_types	List all types in an assembly
analyze_assembly	Get architectural overview of an assembly
get_type_members	Get complete API surface of a type
find_type_hierarchy	Find inheritance relationships
search_members_by_name	Search for members by name
find_extension_methods	Find extension methods for a type

Configuration

The server can be configured via environment variables:

• ILSpy__MaxDecompilationSize: Maximum size of decompiled code in bytes (default: 1048576 = 1 MB)
• ILSpy__DefaultTimeoutSeconds: Default timeout for operations in seconds (default: 30)
• ILSpy__MaxConcurrentOperations: Maximum number of concurrent operations (default: 10)

Architecture

This server follows a clean architecture with clear separation of concerns:

• Domain: Core business logic and entities
• Application: Use cases and application services
• Infrastructure: External system adapters (ILSpy, file system)
• Transport: MCP protocol layer

Security

• All operations are read-only (no file modifications)
• Assembly path validation
• Timeout and cancellation support
• Request context propagation

License

MIT — see LICENSE for details.