Amazon Product Advertising API Developer's Manual page 142

Product Advertising API Developer Guide
Shopping Cart Concepts
Cart Limitations
A cart can contain up to 50 entries. Each entry can represent one or more (up to 999) of the same items.
That means that a Product Advertising API shopping cart can contain a maximum of almost 50,000 items.
Many products have a limit on the quantity that can be added to a cart. Sometimes this is inherent to the
product, for example, one-of-a-kind jewelry items. Sometimes it is a limit set by the vendor, for example,
they might set a limit on big ticket items, such as a motorcycle, of one per customer. If you add an item
to the cart with a quantity that exceeds the maximum allowed, CartAdd automatically resets the quantity
to the maximum value. No error is generated. Therefore, you must verify the quantity of items in the cart
with the number ordered to determine if the quantity has been capped. If so, you must notify the customer.
Active and SaveForLater Areas
Shopping carts have two distinct areas:
• Active—Contains the items that are ready to be purchased.
• SavedForLaterItem—Contains items that a customer has chosen to buy but are currently unavailable,
or items that a customer has designated they want to save and buy later.
Available items placed in a shopping cart are automatically added to the Active area unless the customer
specifies otherwise. Unavailable items or items in the shopping cart that become unavailable are
automatically put into the SaveForLater area. When those items become available Amazon automatically
moves the items to the Active area of the shopping cart.
The SaveForLater area can also be used by customers as a holding place for items they are interested
in but not ready to purchase. The prices and availability for items in this area are regularly updated by
Amazon.
Items That Cannot Be Added to the Active Cart Area
Product Advertising API operations sometimes return items that cannot be added to the Active cart area.
The following sections explain those cases:
• Out of stock items
• Items with limited quantities
• Variation parent items
• Collection parent items
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