This guide will contain some information about the Community D3 API. Remember that you can try out the API (after creating an application) on the API Docs page.
In a D3 character profile items are displayed with only the information needed to show them on a character paper doll (without stats or other tooltip info). In order to get an items stats you need to use the tooltipParam field as an argument to the /data/item API. This will interpret the tooltipParam information and show the item's rolls.