I actually considered using card forge when I started this. I mostly didn't end up using it because of how much more work it would have been.

But also with a rules engine, you have to manually go though every step, and pass priority after every action.

I think it makes more sense to let an LLM play magic like a person would. On early turns it is acceptable to say "I play a land and pass" without going through every phase. And you can say "I tap all my land and play this card" without having to use a tool call and agent turn for every land tap.

Also card forge would not let you goldfish a deck. You must have opponents.

Those things sound less like general problems with rules engines and more like deficiencies of card forge IMO.