How do you define mechanics and features? This is very important for the success of the development. Many times, we think that just talking about something makes that clear for anyone. This is the most common mistake of inexperienced game designers.
“It’s simple, the character moves with the stick and shoots with the right trigger!”
With this sentence I have a gameplay in my mind and you have another.
You should really make the effort of empathizing with the people you are speaking with. Be as visual as possible. 60% visuals, 30% multimedia and only 10% written content is what I try to follow. It is better to speak on something visual and then find and solve all the related problems.
Often, the things we define will require some further set up. Maybe you will have to decide the speed of something. Maybe the odds for some reward. The best way to communicate this is to show clearly how you would like to set up the things, in the engine you are using or in some spreadsheet!
Do them a favor: speak about your needs!