If you initiate the development process with just a general outline of your project and no clarification on the details, there is a good possibility that the finished product will have little resemblance to your concept. Obviously, your team of development can’t read your mind, only thing that they can do is follow what you put down in the specification. Anything else that you don’t add in the specification, it is a fair game for them to interpret in their own way. If it gets worse, you won’t be able to prove that didn’t develop the app you wanted because you never wrote down your requirements in detail.