How do the models know the rules of the game? Are they just supposed to use the MCP tools to figure it out? (Do they have to keep doing that from scratch?)

They were trained on the entire Internet, so they've basically picked up the rules by osmosis. They're fuzzy on specific cards and optimal strategy, but they pretty much know out-of-the-box how the game works, the same as if you went to ChatGPT and asked it a Magic rules question. I don't have any "comprehensive rules" MCP tools or explanation in the context or anything like that.