You can now see the variant grouping information on the APIs as well.
A new API “Get item count by groups” can be used to get information on the variant group id and the count of variants items in the group. The existing APIs (Catalog Search, Get an item, Get all items) can return variant group id and the variant grouping information (is primary, grouping attributes and grouping values). The Catalog Search will require an additional query added to the API call to return the item variant information.
On April 17, the variant information will be updated in all responses for Catalog Search API, Get an item API, and Get all items API. The information will be there irrespective of the variant group id query parameter is present or not.
For more information, see the Items API.