Craft Commerce ajax add to cart, missing information
As Brad said in his answer, what you get back is the lineItem details - enough to update e.g. your totals, shipping quote etc.

The URL of the product, and the product fields etc, are not available in the JSON.  But it's hard to see why they would need to be - you're sending this ajax call from somewhere you already have a reference to the product/variant in your twig templates - why would you need this info repeated in the return object?

If you really need that stuff at that point, you're probably better off ajax loading in a twig template to get at the full product stuff.  If you could clraify what you're actually trying to do I can probably help better/describe what we've done.