We have enhanced the Product update endpoint to support variants. Now it is possible to specify the most important variant parameters including variant parameters.
It is important to mention the variant must always be identified by code (even for products without variants, the code must be provided, if array variants[] is used). If the code is not provided or does not exist, a new variant will be created.
It is also possible to change the code itself – item newCode is to be used.
For complete list of request items, check Product update in Apiary, the right-most pane, section “Request” » “Attributes”.