Use it for:
Percolator handles the boring details for you to keep you working on the fun stuff -- Details like:
Most JSON APIs are ridiculously non-standard, sloppy, and inconsistent. If you write another one of those, everyone will laugh at you and you won't be able to eat lunch with the cool kids. Instead, Percolator can help you create surfable JSON-REST APIs with standardized response formats and error messages that might even make your client developers stop plotting your murder.
Percolator includes powerful resource-oriented CRUD support that abstracts the API details even further so that you're only spending your time on your app's core business logic. Alternatively, you could keep hand-coding all that API and CRUD logic over and over, but you might want to ask why you hate yourself so much. We think you're pretty fantastic.