Modifying the Items in a Remote Shopping Cart
Product Advertising API operations give you a lot of flexibility to modify the number of items in a cart. For example, use:
CartAdd—To add new items to a cart.
CartClear—To remove all items from a cart.
CartModify—To increase or decrease the number of items that are already in a cart, and to move items between the Active and the SaveForLater cart areas.
You can use this operation to delete a single item from a cart by setting its quantity to zero.
All of these operations can be used only on an existing remote shopping cart.