Let's look at the following questions that I've encountered many times with my team.
Can we add this feature?
Yes, no, maybe so... This question doesn't really lead to proper answer. The answer is usually a yes but often what you will get is depending on whether the responder likes the idea or not.
How hard is it to add this feature?
This question is a bit better than the previous one but it still has the same problem of limiting the answer. Easy, hard, very hard... It also tends to provoke negative thinking.
What will be the effort to add this feature?
Now this question get me thinking. Many times people asked the previous two questions are actually trying to get an answer to the real question...how to get there? This one is an open-ended question that leads the responder into problem solving.
I believe there are even better ways to ask the same question. You should think about how to ask the right question if you want a desirable results. It will get you more success if the question is properly asked.