Your question is Prioritizing an Ambiguous Feature Spec. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Walk me through a time you had to create a feature specification from incomplete information. What assumptions did you make, how did you prioritize the requirements, and how did you handle stakeholder pushback or changing inputs along the way?