ILSpy-MCP-Server by ARISTODE - MCP Server

ILSpy MCP Server

Model Context Protocol (MCP) bridge that surfaces ILSpy functionality for automated .NET reverse engineering. The server wraps the official ILSpy PowerShell cmdlets and exposes a small set of tools (list types, enumerate methods, decompile C#) over MCP so coordinating agents can reason about managed assemblies when native decompilers are unavailable.

Prerequisites

Follow these steps to prepare the environment (verified against the upstream ILSpy documentation and official installation guides):

Install the .NET 10.0 SDK
- macOS/Linux: download the installer from dotnet.microsoft.com/download/dotnet/10.0 or use Homebrew (brew install --cask dotnet-sdk).
- Windows: use the .NET SDK installer from the same link.
- Verify with dotnet --list-sdks (should show a 10.0.* entry).
Install PowerShell 7+
- macOS: brew install --cask powershell
- Windows/Linux: follow the instructions at https://learn.microsoft.com/powershell/scripting/install/installing-powershell.
- Confirm availability with pwsh --version.
Clone and build ILSpy (per the official README)
```
git clone https://github.com/icsharpcode/ILSpy ../ilspy
cd ../ilspy
git submodule update --init --recursive
dotnet build ILSpy.XPlat.slnf
```
The PowerShell module is emitted at ../ilspy/ICSharpCode.Decompiler.PowerShell/bin/Debug/netstandard2.0/ICSharpCode.Decompiler.PowerShell.dll.
Install MCP server dependencies
```
python -m pip install mcp[server] typer pydantic
```
(Use a virtual environment if preferred.)

Installation

Clone this repository and install the package in editable mode (optional):

cd ILSpy-MCP-Server
python -m pip install -e .

Alternatively, run directly with PYTHONPATH=src.

Configuration

By default the server assumes the sibling ILSpy checkout and PowerShell module described above. To override locations, pass --module-path or --powershell-path arguments (see below).

Environment Variable	CLI Option	Description
`ILSPY_MCP_HOST`	`--host`	Interface to bind (default `127.0.0.1`).
`ILSPY_MCP_PORT`	`--port`	Port for SSE transport (default `8891`).
`ILSPY_MCP_TRANSPORT`	`--transport`	`sse`, `streamable-http`, or `stdio`.
`ILSPY_MCP_MODULE`	`--module-path`	Path to `ICSharpCode.Decompiler.PowerShell.dll`.
`ILSPY_MCP_PWSH`	`--powershell-path`	Path to the `pwsh` executable.

(Transport environment variables are optional; the CLI options take precedence.)

Running the Server

cd ILSpy-MCP-Server
PYTHONPATH=src python -m ilspy_mcp.server \
  --port 8891 \
  --host 127.0.0.1 \
  --transport sse

On startup the server imports the ILSpy PowerShell module to verify prerequisites, then listens for MCP tool calls.

Available Tools

Tool ID	Description
`set_binary_path`	Load a managed assembly (.dll/.exe) for subsequent calls.
`list_types`	Enumerate types; optional comma-separated `kinds`.
`list_modules`	Report module/assembly metadata.
`list_methods`	List methods for a fully qualified type.
`decompile_type`	Return full C# source for a type.
`decompile_method`	Return the C# body for a single method.
`search_strings`	Regex search across decompiled source; returns type hits.

Clients should call set_binary_path once per session before invoking other tools.

Testing

A minimal suite validates the client-side session helpers:

PYTHONPATH=src pytest tests -q

The tests assume the sample managed DLL used during development is available; replace the path in tests/test_session.py if needed.

Repository Layout

src/ilspy_mcp/        # FastMCP server implementation and helpers
tests/                # Basic integration tests using the MCP client wrapper
configs/              # Example MCP client configuration files

Client Configuration Examples

Cursor – copy configs/cursor.json into your Cursor MCP configuration directory and adjust environment variables (e.g., ILSPY_MCP_MODULE) as needed.
Claude Desktop – merge the configs/claude.json snippet with your existing claude_desktop_config.json to register the server under the ilspy-mcp key.

Both examples invoke python -m ilspy_mcp.server with SSE transport and rely on PYTHONPATH=src so the package is importable without installation. Update paths if you are running from a different working directory.

References

ILSpy project: https://github.com/icsharpcode/ILSpy
PowerShell: https://github.com/PowerShell/PowerShell
Model Context Protocol spec: https://modelcontextprotocol.io/