As others have already said, a REST API would be the proper way to go. Not only is it "pure" enough to allow the API to evolve over time, you can find libraries to consume REST APIs on every platform (desktops and mobile devices)
I would also suggest a more "Agile" approach: rather than "initial release" v. "the rest" I think you should try to release early, a very focused set of features, and have sprints to allow you and us to sync. on the best direction for the API. If that's OK, obviously :)
As others have already said, a REST API would be the proper way to go. Not only is it "pure" enough to allow the API to evolve over time, you can find libraries to consume REST APIs on every platform (desktops and mobile devices)
I would also suggest a more "Agile" approach: rather than "initial release" v. "the rest" I think you should try to release early, a very focused set of features, and have sprints to allow you and us to sync. on the best direction for the API. If that's OK, obviously :)