To add to my previous post: it's not like this is a weird concept; every e-commerce site out there implements this. Imagine if we followed the RPC model: the user would click on "submit", and then the browser would wait for a reply when the order was finished being delivered - multiple days later!

Obviously this is impractical, so people follow the natural REST model: they create an Order resource, then send you a link with which you can follow the status of that resource.

But bring the "API" word and suddenly all of the preconceptions push developers to implement everything as function calls.