STS2 Modding Assistant MCP

STS2 Modding MCP

An LLM-powered modding toolkit for Slay the Spire 2. This Model Context Protocol server connects to any MCP-compatible AI assistant — Claude Code, Claude Desktop, Cursor, Windsurf, and more — giving it 151 tools to reverse-engineer the game, generate mod code, build and deploy mods, inspect the live game engine, and autonomously playtest your mods by playing the game itself.

You don't need to be a programmer to use it (though that certainly helps). Use it as a powerful tool for seasoned developers or if you're a beginner, try just describing what you want in plain English and let the LLM handle the code (always prompt it to do extensive testing, debugging and hardening. This is a very important step).

This project is doubling as a fun experiment for me. Please reach out if you have any issues, can't figure something out, want to suggest a feature, or find a bug!

Requirements

• []Slay the Spire 2 (Steam)

  []Python 3. 11+ — python.org/downloads (check "Add to PATH" during install on Windows)

  []. NET 9. 0 SDK — dotnet.microsoft.com

  []An MCP-compatible AI client (Claude Code, Claude Desktop, Cursor, Windsurf, etc.)

  • []GDRE Tools — for extracting Godot assets from the game PCK (download)

    []ilspycmd — for C# decompilation: dotnet tool install -g ilspycmd

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    Installation

    1. Extract the downloaded zip to a folder you'll keep (e.g. C:\sts2-modding-mcp)

    2. Open a terminal in that folder

    3. Create and activate a virtual environment:

    python -m venv venv

    # Windows (PowerShell):

    venv\Scripts\Activate.ps1

    # Windows (cmd):

    venv\Scripts\activate.bat

    # Windows (Git Bash):

    source venv/Scripts/activate

    # macOS / Linux:

    source venv/bin/activate

    4. Install: pip install .

    5. Run first-time setup: python -m sts2mcp.setup

    The setup wizard will auto-detect your game install, install ilspycmd if needed, decompile the game's C# assemblies, and build/deploy the bridge mods to the game's mods folder.

    If your game isn't auto-detected, edit sts2mcp_config.json in the install folder:

    { "game_dir": "D:\\Games\\Slay the Spire 2" }

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