The best thing to do is to start using API that other people have built. Try getting the data, see where the bottlenecks/friction points are - what things are c

The best thing to do is to start using API that other people have built. Try getting the data, see where the bottlenecks/friction points are - what things are clear and what things are not. This will put you in the shoes of someone who will physically use one. Otherwise, its all conjecture.