Metascript is a web application that allows users to generate custom Blender add-ons using a visual drag-and-drop interface. It provides tools to design custom graphical user interfaces utilizing layout elements like rows, columns, labels, and icons. Users can define add-on metadata (bl_info) and assign specific Python functionality by writing Poll, Invoke, and Execute methods for their operators. Finished projects are downloaded as standard ZIP files that can be installed directly into Blender.