This is a script for UndertaleModTool, which can export game files as project files for GameMaker Studio.
Currently compatible with gms1.4, will support gms2 in the future.
Gamemaker 1 files are formatted in XML. The ENIGMA wiki page explains how these work.
Gamemaker 2 files are formatted in JSON.
The script is written in C# using all the libraries included with UMT.