ILSpy MCP Server

MCP server that gives AI assistants .NET decompilation and static analysis capabilities via ILSpy.

Ask your favourite AI Chatbot to explain how to use ILSpy MCP Server:

• What is this?
• Supported MCP Clients
• Install
  • Option A: Pre-built Binary
  • Option B: Build from Source
• Configure Your MCP Client
• How It Works
• Usage Examples
• Available Tools
• Running as an HTTP Server
• Architecture
• Comparison with Other Servers
• Acknowledgements
• License

What is this?

ILSpy MCP Server lets AI assistants decompile, inspect, and analyze .NET assemblies through natural language. It wraps ICSharpCode.Decompiler — the same decompilation engine that powers ILSpy — as a Model Context Protocol (MCP) server. No GUI needed. Your AI assistant calls the decompiler directly and gets back structured results it can reason over.

This means you can do things the ILSpy GUI can't:

• Ask questions in natural language — "What does this method do?" or "Find all types that implement ILogger" instead of clicking through tree views
• Chain analysis across multiple assemblies in a single conversation — trace a call from your app through framework code and into a NuGet package
• Get AI-powered explanations alongside raw decompiled code — the assistant reads the output and explains patterns, potential bugs, or architectural decisions
• Automate bulk analysis — decompile entire namespaces, search across types, and map dependency graphs without manual navigation
• Integrate into any MCP client — Claude Code, Cursor, VS Code, or any tool that speaks MCP

Supported MCP Clients

Works with any MCP-compatible client. We recommend Claude Code.

Amazon Q Developer CLI, Augment Code, Claude, Claude Code (recommended), Cline, Codex, Copilot CLI, Crush, Cursor, Gemini CLI, Kilo Code, Kiro, LM Studio, Opencode, Qodo Gen, Qwen Coder, Roo Code, Trae, VS Code, VS Code Insiders, Warp, Windsurf, Zed, and more.

Install

Option A: Pre-built Binary (Recommended -- no .NET required)

1. Download the latest release for your platform from Releases:

   | Platform | File | |----------|------| | Windows x64 | ilspy-mcp-win-x64.zip | | Linux x64 | ilspy-mcp-linux-x64.tar.gz | | Linux ARM64 | ilspy-mcp-linux-arm64.tar.gz | | macOS x64 | ilspy-mcp-osx-x64.zip | | macOS ARM64 | ilspy-mcp-osx-arm64.zip |

   Each release includes SHA256 checksums (.sha256 files) for verifying download integrity.

2. Extract the archive:

   Windows (PowerShell):

   Expand-Archive ilspy-mcp-win-x64.zip -DestinationPath ilspy-mcp
   

   Linux:

   tar -xzf ilspy-mcp-linux-x64.tar.gz -C ilspy-mcp
   chmod +x ilspy-mcp/ILSpy.Mcp
   

   macOS:

   unzip ilspy-mcp-osx-arm64.zip -d ilspy-mcp
   chmod +x ilspy-mcp/ILSpy.Mcp
   

3. Continue to Configure Your MCP Client below.

Option B: Build from Source

1. Clone the repository:

   git clone https://github.com/cervonwong/ILSpy-MCP.git
   cd ILSpy-Mcp
   

2. Build the project:

   dotnet build
   

3. The binary is at src/ILSpy.Mcp/bin/Debug/net10.0/ILSpy.Mcp. Use this path when configuring your MCP client below.

Configure Your MCP Client

Pick your client and follow the steps.

Claude Code

1. Run:

   claude mcp add ilspy-mcp --command "/path/to/ilspy-mcp/ILSpy.Mcp" --scope user
   

2. Restart Claude Code. The tools are now available.

Cursor

1. Add to your MCP settings JSON:

   {
     "mcpServers": {
       "ilspy-mcp": {
         "command": "/path/to/ilspy-mcp/ILSpy.Mcp",
         "args": []
       }
     }
   }
   

2. Restart Cursor.

Claude Desktop

1. Add to claude_desktop_config.json:

   {
     "mcpServers": {
       "ilspy-mcp": {
         "command": "/path/to/ilspy-mcp/ILSpy.Mcp",
         "args": []
       }
     }
   }
   

2. Restart Claude Desktop.

How It Works

You don't interact with ILSpy MCP directly. Your MCP client (Claude Code, Cursor, etc.) launches and communicates with it automatically in the background.

To analyze a .NET assembly, just mention the full path to the DLL in your chat. The AI assistant will call the appropriate ILSpy tools for you.

Usage Examples

Ask your AI assistant to work with .NET assemblies using natural language. Replace the paths with actual DLL paths on your machine:

• Decompile a type -- "Decompile the String class from C:\Program Files\dotnet\shared\Microsoft.NETCore.App\10.0.0\System.Runtime.dll"
• List all types -- "List all types in C:\Users\me\projects\MyApp\bin\Debug\net10.0\MyLibrary.dll"
• Find a method -- "Find the CalculateTotal method in D:\libs\Calculator.dll"
• Decompile a constructor -- "Decompile the .ctor constructor of UserService in C:\repos\MyApp\bin\Debug\net10.0\MyApp.dll"
• Analyze type hierarchy -- "Show me the type hierarchy for ProductService in C:\repos\ECommerce\bin\Release\net10.0\ECommerce.dll"
• Search members -- "Search for members containing 'Authenticate' in C:\repos\AuthService\bin\Debug\net10.0\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 or constructor (.ctor/.cctor) | | 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 (constructors, methods, properties, fields, events) | | find_type_hierarchy | Find inheritance relationships | | search_members_by_name | Search for members by name | | find_extension_methods | Find extension methods for a type |

Running as an HTTP Server (Remote / VM)

By default the server uses stdio — the MCP client launches it and communicates via stdin/stdout. For remote access (e.g. running on an analysis VM while the MCP client runs on your workstation), switch to HTTP mode.

Starting the HTTP server

Pick whichever matches how you installed it:

Pre-built binary:

# From the directory where you extracted the release archive
./ILSpy.Mcp --transport http        # Linux / macOS
.\ILSpy.Mcp.exe --transport http    # Windows

From source:

# From the repo root (where ILSpy.Mcp.csproj lives)
dotnet run -- --transport http

The server starts and prints:

ILSpy MCP server listening on http://0.0.0.0:3001

It stays running in the foreground until you stop it (Ctrl+C).

Connecting your MCP client

From the machine running your AI assistant, point the MCP client at the server's HTTP endpoint. Replace analysis-vm with the server's hostname or IP:

Claude Code:

claude mcp add ilspy-mcp --transport http http://<analysis-vm>:3001/mcp --scope user    # available across all your projects
claude mcp add ilspy-mcp --transport http http://<analysis-vm>:3001/mcp --scope project # shared with team via .mcp.json in repo
claude mcp add ilspy-mcp --transport http http://<analysis-vm>:3001/mcp --scope local   # current project only (default)

Claude Desktop / Cursor (MCP settings JSON):

{
  "mcpServers": {
    "ilspy-mcp": {
      "type": "http",
      "url": "http://<analysis-vm>:3001/mcp"
    }
  }
}

Changing port and host

| Setting | Default | CLI | Env Variable | appsettings.json | |---------|---------|-----|--------------|------------------| | Transport | stdio | --transport http | ILSPY_TRANSPORT=http | Transport:Type | | Port | 3001 | — | Transport__Http__Port | Transport:Http:Port | | Host | 0.0.0.0 | — | Transport__Http__Host | Transport:Http:Host |

Transport mode is resolved in priority order: CLI arg > env var > appsettings.json.

To make HTTP the permanent default, edit appsettings.json (located next to the binary):

{
  "Transport": {
    "Type": "http",
    "Http": {
      "Port": 3001,
      "Host": "0.0.0.0"
    }
  }
}

Running as a background service

To keep the server running after you disconnect from the VM:

Linux (systemd):

# /etc/systemd/system/ilspy-mcp.service
[Unit]
Description=ILSpy MCP Server
After=network.target

[Service]
ExecStart=/path/to/ILSpy.Mcp --transport http
Restart=on-failure
User=youruser

[Install]
WantedBy=multi-user.target

sudo systemctl enable --now ilspy-mcp

Windows (Task Scheduler or sc.exe):

# Quick background run with nohup equivalent
Start-Process -NoNewWindow -FilePath .\ILSpy.Mcp.exe -ArgumentList "--transport http"

Docker / tmux / screen also work — the server is a single self-contained binary with no external dependencies.

Security

No authentication is built in. The server binds to 0.0.0.0 (all interfaces) by default. Protect it with:

• Firewall rules limiting access to trusted IPs
• A reverse proxy (nginx, Caddy) adding TLS and/or auth
• VPN or SSH tunnel between client and server
• Binding to 127.0.0.1 and using SSH port forwarding

Architecture

The server follows a clean layered architecture: Domain (core entities), Application (use cases), Infrastructure (ILSpy and file system adapters), and Transport (MCP protocol layer). All operations are read-only -- the server never modifies files on disk.

Comparison with Other .NET Decompilation MCP Servers

Several projects expose .NET decompilation over MCP. Here's how ILSpy MCP Server compares:

| | ILSpy MCP Server | DnSpy-MCPserver-Extension | DecompilerServer | ilspy-mcp-server | @iffrce/mcp-dotnetdc | |---|---|---|---|---|---| | Engine | ICSharpCode.Decompiler (actively maintained) | dnSpyEx (community fork of abandoned dnSpy) | ICSharpCode.Decompiler | ILSpy CLI (ilspycmd) | ILSpy CLI (ilspycmd) | | Runtime required | None (self-contained binary) | .NET + dnSpyEx install | .NET 10 | Python 3.8+ and ILSpy CLI | Node.js and ILSpy CLI | | Install options | Pre-built binary or source | Clone + build | Clone + build | pip install | npm install | | Transport | stdio + HTTP (remote/VM support) | SSE or stdio | stdio | stdio | stdio | | Cross-platform | Windows, Linux, macOS (x64 + ARM64) | Windows only (dnSpyEx dependency) | Windows, Linux, macOS | Depends on ILSpy CLI availability | Depends on ILSpy CLI availability | | Architecture | Clean layered (Domain/Application/Infrastructure/Transport) | dnSpyEx plugin | Single project | Python wrapper around CLI | Node.js wrapper around CLI | | Type decompilation | Yes | Yes | Yes | Yes | Yes | | Method decompilation | Yes (including .ctor/.cctor) | Yes | Yes (member-scoped snippets) | No | No | | Type hierarchy analysis | Yes | No | No | No | No | | Extension method discovery | Yes | No | No | No | No | | Assembly architecture overview | Yes | Yes | No | Yes | No | | Member search | Yes | Yes | Yes | No | No | | Multi-version comparison | No | No | Yes | No | No | | Read-only by design | Yes (never modifies files) | Has renaming/edit capabilities | Yes | Yes | Yes |

Why ILSpy MCP Server?

• Zero-dependency install. Download a single self-contained binary — no .NET SDK, no Python, no Node.js, no ILSpy CLI to install separately. It just works.
• Actively maintained engine. Built on ICSharpCode.Decompiler, the same library that powers ILSpy — under active development with regular releases. Not dependent on abandoned tools like dnSpy.
• Remote analysis via HTTP. Run the server on an analysis VM or build server and connect from anywhere. No other .NET decompilation MCP server supports this out of the box.
• True cross-platform support. Pre-built binaries for Windows, Linux, and macOS on both x64 and ARM64. No Windows-only dependencies.
• Direct engine integration. Calls the decompiler library in-process for maximum speed and fidelity. No shelling out to CLI tools, no parsing text output, no intermediate formats.
• Safe by design. Every operation is read-only. The server never writes to disk, never modifies assemblies, never executes the code it analyzes.

Acknowledgements

Forked from bivex/ILSpy-Mcp.

License

MIT -- see LICENSE for details.

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< Built with love by a fellow analyst :) 💖 >
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