"But I am tall!"
Translation:하지만 저는 키가 커요!
Since I've seen the phrase "I'm tall" worded like this before, I'd say yes. Otherwise, it sounds like you're saying "I'm big" since the verb 크다 (conjugated in the present tense as 커요) means "to be big". When used as a noun (키가), it becomes one way of saying "height". When combining both words you get, for example, "건물은 키가 커요", which translated word for word means "the height if the building is big," which you can then take to mean "the building is tall."