DecompilerServer

DecompilerServer is an MCP server that decompiles and analyzes .NET assemblies. You connect it to your AI coding tool (Claude Desktop, Cursor, VS Code, Codex, etc.) and it lets the AI read, search, and compare .NET code — even across different versions of an assembly.

This is a particularly strong LLM use case because so much real-world .NET behavior lives in binaries the model cannot inspect on its own: third-party libraries, game assemblies, internal builds, and older releases. By giving the model direct decompiler-backed access to those assemblies, you turn "I only see the source in this repo" into "I can inspect the actual code that runs", which makes reverse engineering, migration work, debugging, and version-to-version analysis much more effective.

Common use cases: general .NET assembly inspection, Unity Assembly-CSharp.dll workflows, and multi-version browsing such as RimWorld mod porting.

Already familiar with .NET and MCP? Skip to Advanced Guide for build-from-source instructions, full tool reference, and development details.

Quick Start

This section helps you install DecompilerServer and connect it to your MCP client in a few steps.

What You Need

.NET 10 runtime — the prebuilt release binaries depend on it. Download and install the runtime for your platform before continuing.

Step 1 — Download

Go to the latest release and download the archive for your platform:

Extract the archive to a folder you can remember (for example ~/tools/decompiler-server).

Expand-Archive decompilerserver-v*-win-x64.zip -DestinationPath "$HOME\tools\decompiler-server"

mkdir -p ~/tools/decompiler-server
tar -xzf decompilerserver-v*-*.tar.gz -C ~/tools/decompiler-server --strip-components=1

Step 2 — Configure Your MCP Client

Add DecompilerServer to your MCP client configuration. Replace the path below with the actual location where you extracted the files.

{
  "mcpServers": {
    "decompiler": {
      "command": "/absolute/path/to/DecompilerServer"
    }
  }
}

{
  "mcpServers": {
    "decompiler": {
      "command": "C:\\tools\\decompiler-server\\DecompilerServer.exe"
    }
  }
}

{
  "mcpServers": {
    "decompiler": {
      "command": "/absolute/path/to/DecompilerServer"
    }
  }
}

{
  "servers": {
    "decompiler": {
      "type": "stdio",
      "command": "/absolute/path/to/DecompilerServer"
    }
  }
}

[mcp_servers.decompiler]
command = "/absolute/path/to/DecompilerServer"

[mcp_servers.decompiler]
command = "dotnet"
args = ["/absolute/path/to/DecompilerServer/bin/Release/net10.0/DecompilerServer.dll"]

Step 3 — Use It

Once connected, ask your AI assistant to load and explore assemblies. For example:

"Load the assembly at /path/to/MyLibrary.dll and search for types that contain Controller."

The assistant will use DecompilerServer tools automatically. It can load assemblies, search types, decompile source, compare versions, and more. See the Workflow Reference for the full list of operations.

Troubleshooting

Advanced Guide

This section covers building from source, the full set of MCP launch options, the complete tool workflow, and contributor information.

Highlights

• Load assemblies directly with assemblyPath or use Unity-friendly gameDir loading.
• Keep multiple assemblies loaded at once under aliases such as rw14, rw15, and rw16.
• Use memberId follow-up tools without repeatedly resupplying the alias; routing uses the member ID's MVID.
• Compare aliases structurally with compare_contexts, then drill into types or members with compare_symbols.
• Diff individual method bodies with compare_symbols(..., compareMode: "body").
• Decompiled non-type member source is returned as a member-scoped snippet rather than a whole containing type.

Requirements

• .NET 10 runtime for release assets or built output
• .NET 10 SDK if you want to build from source

Build from Source

git clone https://github.com/pardeike/DecompilerServer.git
cd DecompilerServer
dotnet build DecompilerServer.sln -c Release
dotnet run --project DecompilerServer.csproj -c Release

MCP Client Launch Options

Framework-dependent build output (requires dotnet on PATH):

command: dotnet
args:
  - /absolute/path/to/DecompilerServer/bin/Release/net10.0/DecompilerServer.dll

Native app host from dotnet build:

• macOS/Linux: /absolute/path/to/DecompilerServer/bin/Release/net10.0/DecompilerServer
• Windows: C:\\absolute\\path\\to\\DecompilerServer\\bin\\Release\\net10.0\\DecompilerServer.exe

Native app host from dotnet publish:

• macOS/Linux: /absolute/path/to/DecompilerServer/bin/Release/net10.0/publish/DecompilerServer
• Windows: C:\\absolute\\path\\to\\DecompilerServer\\bin\\Release\\net10.0\\publish\\DecompilerServer.exe

Release assets are packaged as framework-dependent single-file executables and still require the .NET 10 runtime.

Workflow Reference

Load one or more assemblies:

load_assembly({
  "assemblyPath": "/path/to/rw14/Assembly-CSharp.dll",
  "contextAlias": "rw14"
})

load_assembly({
  "gameDir": "/path/to/rw16",
  "assemblyFile": "Assembly-CSharp.dll",
  "contextAlias": "rw16"
})

Inspect loaded aliases:

list_contexts({})
status({})

Search and decompile:

search_types({
  "query": "Pawn",
  "limit": 10,
  "contextAlias": "rw16"
})

get_decompiled_source({
  "memberId": "<member-id-from-search>"
})

Once you have a memberId, follow-up tools normally route to the correct loaded assembly automatically.

Compare aliases:

compare_contexts({
  "leftContextAlias": "rw14",
  "rightContextAlias": "rw16",
  "namespaceFilter": "Verse",
  "deep": true
})

compare_symbols({
  "leftContextAlias": "rw14",
  "rightContextAlias": "rw16",
  "symbol": "Verse.Root_Play",
  "symbolKind": "type"
})

compare_symbols({
  "leftContextAlias": "rw14",
  "rightContextAlias": "rw16",
  "symbol": "Verse.Pawn:Kill",
  "symbolKind": "method",
  "compareMode": "body"
})

Development

dotnet format DecompilerServer.sln
dotnet test -c Release --no-restore

Releasing

The GitHub Release workflow is triggered by pushing a tag that starts with v and matches the project version in DecompilerServer.csproj.

For example, if the project version is 1.3.3:

git tag -a v1.3.3 -m "Release v1.3.3"
git push origin v1.3.3

Documentation

• README.md: user-facing overview and quick start
• ARCHITECTURE.md: durable technical reference (implementation details, routing, compare semantics, testing)
• TODO.md: backlog and future work

If you are changing implementation details, tool-routing behavior, compare semantics, or test patterns, update ARCHITECTURE.md rather than creating a new standalone guide.