"Is it bad?"
Translation:An bhfuil sé go dona?
An bhfuil sé? and An ea? are both translated as "Is it?" in English, but they aren't equivalent. Irish uses the Copula in certain situations, and the verb bí in other situations, whereas English uses the verb "be" for both.
This can be confusing for learners, but it's pretty fundamental (it's covered in the Tips & Notes for the very first Skill (Basics 1).
This is not a Copula style sentence, so you can't use An ea to ask this question.