Question

______ ? He's tall and thin.

Answer 1

Thank you for asking the question!
If such kind statement is the answer then it clearly hints towards the question which is being asked about the looks of a person. there can be multiple ways to ask the question!
How does he look like?
What is he like?
What is his figure?
Hope it helps.

Answer 2

‘How is his build’?  

The question for the answer ‘He’s tall and thin’ should be ‘How is his build?’. Since the answer suggests the proportions of the person’s body, the question is designed so. It is also clear that the person in question is a male, as the answer shows it as a ‘he’