I'd really love some kind of unified interface for program input.

Like, a Python program, a Ruby program, an online form, a REST API, and so on, all specify the input they need in ways specific to each tool (selecting from a predefined list is `CHOICES` param for argparse, a dropdown for a web form, etc). Why can't we just have some JSON spec for "input"? A list of params, each with a name, a description, a type, perhaps a list of possible choices -- the same sort of thing `argparse` exposes as its API.

Then, depending on the need, we can render that into a web page, or a parser, or whatever, and we can build libraries that can always expect to get input the same way without needing to redefine it all for each interface. Does something like this exist already and I just haven't seen it?