Mickey has no idea what 'cantrip' is but he does not care. He does care that Taako essentially said yes.

"YAHOO!" Mickey literally jumps for joy, like a little kid finding their favorite toy under the Christmas tree. "Oh, thank you, thank you, thank you! I won't let you down, that's a promise! And if there's ever anything I can do for you in return, you just say the word!"

Yaaay, the exciting world of magic school is beginning! He's going to fight bad guys and protect everyone and when he goes home he can teach his friends and everyone will think he's super cool and maybe the princess will think he's super cool...