Compare all the product could be against the core idea, realize what is really necessary, what has no purpose, what has no purpose just yet, and in which phase the purpose will be generated. We have the concept now, we can realize what delivery phases can be, what is their order of priority, what is a must, what is a decoration that may or may not be needed and when and how you can know that.
Key deliverables:
A definitive decision of what MVP will consist of.
Brief description of each of the screens that visually define the functionality.