Hi! OP here.

This actually works out okay for most of our libraries. For the ones that can support it (Ruby, Python, etc), we don't hardcode the properties for any resources and instead generate objects on-the-fly when you make an API request.

In the $1 example, the libraries will just construct a Charge object without the `amount` property, since it wasn't returned in the API response.

You're right that it isn't perfect for other languages, though. We're working on making our versioning story better in our docs, libraries, webhooks, etc. (: