"I am clear."
I think it's because "mir" is used in a different case. For example, you can say Ich bin klar" (if that sentence is correct), but you can't say "Ich bin heiss", because that means something much different than "Mir ist heiss". It's just a different case since German has 4 (Nominativ, Akkusativ, Dativ, Genativ). I believe "mir" is the dativ case.