Universal Game Modder MCP Server

Universal Game Modder

One MCP server to inspect and mod any game — driven by an AI agent.

Universal Game Modder (UGM) is a local Model Context Protocol server that gives an AI agent (like Claude in Claude Code) hands for game reverse-engineering and modding: it auto-detects a game's engine, then exposes a toolset for analyzing and patching the binaries — all running locally on your own machine, no cloud, no telemetry.

This is the free open-core edition (v0.1.3).

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⚠️ Responsible-use notice

UGM is a general-purpose binary-analysis and interoperability tool. It is meant for modding, interoperability, security research, and education on software you legally own or are authorized to analyze. You are responsible for how you use it. Before installing, read ACCEPTABLE_USE.md and LICENSE-EULA.md.

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What's in the free edition

• One stdio MCP server that an agent connects to and drives.
• Game-engine auto-detection — point it at a game directory; it identifies Unity (Mono / IL2CPP), Unreal, Godot, Java, and native binaries from file signatures.
• Native binary analysis + patching toolset — PE header analysis, hex read/write/search/replace, IDA-style pattern scanning, string extraction, checksums, and binary diffing, running natively in-process (no external tools required).

The guided game-modder workflow skill and the delegated decompilation backends land in a later release; this edition is the MCP server + engine detection + the native toolset.

Not in the free edition (Pro tier)

The web dashboard, the delegated Unity/Unreal/JAR decompilation backends, and native disassembly are part of the Pro tier and are not included here. The free edition is fully functional on its own for engine detection and native binary work.

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Requirements

• Node.js 18+ (uses ES modules and better-sqlite3)
• Claude Code or any MCP-capable client
• Windows / macOS / Linux (native tools are cross-platform; the smallest cut ships no OS-specific binaries)

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Install

# from the repo root
./setup.ps1

Or manually (dist/ ships prebuilt; there is nothing to compile in this edition):

npm install

Then register the server with your MCP client. For Claude Code, add to your MCP config:

{
  "mcpServers": {
    "universal-game-modder": {
      "command": "node",
      "args": ["dist/index.js"]
    }
  }
}

On first run, ugm.config.json ships with empty placeholders — the free edition needs no external paths. (The Pro delegate backends are where those get filled in.)

Config resolution

The server reads the first of these that exists and merges it over built-in defaults:

1. the file named by the UGM_CONFIG environment variable
2. ugm.config.local.json next to package.json — your machine-specific paths; keep it out of version control (the repo's .gitignore already does)
3. ugm.config.json — the tracked file, placeholders only

So you can fill in backend paths without ever editing a file that could end up in a release or a pull request.

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Quickstart

Once connected, ask your agent to work through these. Every example below is executed against a real binary before each release — see Verified examples.

Parameter naming: file-level tools take file_path (and file_path_a / file_path_b for comparisons). Game-directory tools take game_path. Disassembly tools take binary_path.

1. Detect what a game is built with:

detect_engine  { "game_path": "C:\\Path\\To\\Game" }

2. Set it as the active target:

load_game  { "game_path": "C:\\Path\\To\\Game" }

3. Analyze a binary:

analyze_file_format  { "file_path": "...\\SomeBinary.dll" }   # magic bytes, managed vs native
analyze_pe_full      { "file_path": "...\\SomeBinary.exe" }   # PE headers, sections, data directories

4. Search and inspect:

extract_strings          { "file_path": "...", "min_length": 8 }
extract_dll_classes      { "file_path": "...", "search_terms": ["Health","Damage"] }
pattern_scan             { "file_path": "...", "pattern": "48 8B ?? ?? ?? ?? ??" }
search_binary_pattern    { "file_path": "...", "patterns": ["maxHealth"] }

5. Patch and verify:

hex_read       { "file_path": "...", "offset": 4096, "length": 64 }
hex_replace    { "file_path": "...", "search_hex": "90 90", "replace_hex": "EB 00" }
calculate_checksums       { "file_path": "..." }              # before/after integrity
compare_binaries_detailed { "file_path_a": "...", "file_path_b": "..." }

6. Disassemble (native, included):

disassemble_function  { "binary_path": "...\\SomeBinary.exe", "rva": 4096 }
disassemble_range     { "binary_path": "...\\SomeBinary.exe", "rva": 4096 }

Full free-edition tool list

These 29 tools run entirely in-process and need no external backend.

Native binary tools (19) — all take file_path unless noted: Detection / PE: analyze_pe_full, analyze_file_format, analyze_dll_structure, rva_to_offset (+rva), offset_to_rva (+offset) Hex: hex_read (+offset), hex_write (+offset,hex_data), hex_search (+hex_pattern), hex_replace (+replace_hex) Scanning: pattern_scan (+pattern), pattern_scan_all (+pattern), search_binary_pattern (+patterns) Strings / classes: extract_strings, extract_strings_advanced, extract_dll_classes Integrity / diff: calculate_checksums, compare_binaries_detailed (file_path_a,file_path_b) Godot: analyze_godot_pck Disassembly: disassemble_function (binary_path,rva)

Workflow / session tools (10): detect_engine, load_game, game_status, find_steam_games, mod_this_game, find_gameplay_values, build_and_deploy, debug_mod, scaffold_mod, list_available_tools

What the server also lists (Pro backends)

For transparency: the server advertises 100 tools total. The other 64 are the Unity (27), Unreal (11), and Java/JAR (26) decompilation suites, which route to external Pro-tier backend executables. They appear in the tool list, but calling one without a configured backend returns a clear error:

ERROR: Backend unity-decompiler not configured (missing executable path)

That is expected behavior in the free edition, not a defect. Configure their paths in ugm.config.json (Pro) to enable them.

Verified examples

The Quickstart calls above are not aspirational. Each release is gated on a verification pass that executes them against a real PE binary and requires every one to return real data. The v0.1.3 pass (2026-09-02, on the restored release cut) ran the gate's 20 documented calls plus 3 clean-failure checks; results are recorded in VERIFICATION.md.

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License

The UGM code is released under the MIT License. Use of the tool is additionally governed by LICENSE-EULA.md and ACCEPTABLE_USE.md. Third-party components used by the Pro-tier backends are attributed in licenses/.

Changelog

See CHANGELOG.md. Current version: v0.1.3 — the config can no longer ship machine paths, and the release was restored and re-verified after a disk incident. v0.1.2 fixed engine detection; v0.1.1 fixed the docs and added the gate.