A basic implementation of this service would take less than 100 lines in any language commonly used on the web.
So if you're generating json, it's advisable to wrap it so that parsers written according to the older specs won't choke on it.
However, when parsing, like this, you want to try and accept values.
Nice presentation though, the site looks nice.
EDIT: I see you can create and update through the HTTP API, which makes it much more useful.
Here's a simple screencast: http://crudzilla.com/assets/img/info-graphics/instantiator.g...
There's a lot that you can with it, in terms of generating JSON.
It would be cool to be able to drag and drop an excel document into here and call it with a url.