Iām not sure if I understand correctly or you looking at using API wrong way but API calls are made from app you are using for example postman or something similar. You do not need to store json.
Maybe it would worth to have a look at documentation here: https://docs.google.com/document/d/1q6i417-N3cYUxDdX0FLi__T9l-RZ0gpuVQbJA5VgDxc/edit