Consider this: you are API integrator and you have no idea which fields users custom form contains. You would like to present to user of your tool list of forms presented on particular site and it's fields. The user then could decide what to do with data of particular form. Right now, it's impossible to do that without bothering the user to enter those form definition information again in integrators tool. Ideal case is, where this integration tool will already have the information about the form and let user ONLY select the action which will be applied on those.
an example of curl call of such endpoints attached