I would like to write some rules for a game I have in head but I don't know how to do that. So are there some methodologies or modeling tools (like UML) to do that? I'm thinking about a kind of tree of competencies or some kind of map to be sure that the game is well balanced.

I always wonder how the team who imagines some powers in magic the gathering for example does it. Do they have some diagrams to be sure the powers or creatures they imagine are well balanced for the entire game?

I'm pretty noob in the game creation so I'll be happy with some directions to seek.. Technical terms or basic principles to learn.

Thanks for help.