You mentioned that it should be available on as many platforms as possible.
So does that counts Browser extensions? Or Plugins?
Framework to create specific mechanics? Like a platformer player script in godot or a demo project in unity that you can then use to build more of your game.
And about availability if the tool is a python script that you would need a text editor to run. Would that count as a tool?
Or, anything other than a game counts as a tool? Such as if you can categorize it as a tool on itch.io then it's a tool. Which would include the demo projects to build your games around them however.
Because if it's a project file or code to build your game from, then it would be a game just not as an executable but in a project file that can only be opened in a specific game engine.
I get it if it's hard for you to answer so just tell me if I can submit my platformer character script for the godot engine lol.