This is just a prototype, but it is an attempt to solve a big problem I've had: describing a schema to a remote client system (browser / mobile / etc) in a portable way.
Sure, I could just use a traditional form library to render HTML (such as wtforms, etc), but what if my client doesn't understand HTML? Or even if it is a browser - what if my template system resides on the client side (in javascript), and I don't want to make presumptions about how my javascript chooses to render the form on the server side.
JSON Schema (http://json-schema.org/) provides a way to describe schemas in a language / system agnostic way.