dnSpy MCP

MCP server exposing dnSpy decompilation — search, list members, decompile to C#, and get IL from .NET assemblies. A Python (FastMCP) shim supervises a .NET decompiler worker built from this dnSpy fork; the published wheel bundles the worker, so installing needs no .NET build.

Use (Windows)

claude mcp add dnspy -- uvx dnspy-mcp

or pip install dnspy-mcp. That's it — the worker ships inside the wheel.

Tools

• search_symbols(assembly, query, kind?) — kind: type | method | field | any
• list_members(assembly, typeFullName)
• decompile_type(assembly, typeFullName)
• decompile_method(assembly, typeFullName, method) — method = name or 0x-token
• get_il(assembly, typeFullName, method)

assembly is an absolute path; the worker loads + caches it on first use.

Develop

git submodule update --init Extensions/ILSpy.Decompiler/ICSharpCode.Decompiler Extensions/ILSpy.Decompiler/NRefactory
dotnet build dnSpy.Mcp.Worker/dnSpy.Mcp.Worker.csproj -c Release
cd mcp && py -m pip install -e ".[dev]"
$env:DNSPY_WORKER_EXE = "<repo>/dnSpy.Mcp.Worker/bin/Release/net48/dnSpy.Mcp.Worker.exe"
py -m pytest -q

DNSPY_WORKER_EXE overrides the bundled worker path for development.

Publish

# set $env:TWINE_USERNAME='__token__'; $env:TWINE_PASSWORD=<pypi-token>
powershell -ExecutionPolicy Bypass -File mcp/publish.ps1