that is the ultimate debate on this site, i must say.
honestly, i dont really think there is a way. its completely up to the reader to say if it is fluffy or not. somebody obviously posted it with the utmost belief that it wasnt fluffy, but it is typecast as fluffy.
all im saying is, it is completely up to you. some spells i know are comepletely fluffy because it is very impossible to achieve the goal in the real world. like the "grow wingz" spell. sure, your spirit MIGHT grow wings, but you yourself will not.
it is completely up to you to decide the difference between fluff and no fluff.
hope this helps.