You might assume that any item returned by one of Product Advertising API's search operations is for sale. This, however, is not the case. Some items, such as Variation parents and Collection parents, are never for sale. Before presenting items to customers, you must make sure the items can be purchased.

Product Advertising API provides several ways to determine if an item can be purchased, for example, ItemSearch has an Availability parameter, which specifies whether an item is available for purchase. The best way, however, to determine whether or not an item can really be purchased is by using one of the following response groups in a request:

	Note
	Large is a parent of the Offers response group.

All of the search operations listed, except BrowseNodeLookup, can use these response groups. These response groups return an OfferListingId element for each item that can be purchased. Items that do not have an OfferListingId cannot be purchased.

The following response snippet shows that an item can be purchased because the response contains an OfferListingId.

<Item>
  ...
  <Offer>
    ...
    <OfferListing>
      <OfferListingId>g7CWSnBZmVESKy%2BCNS</OfferListingId>
      <ExchangeId>Y01Y4038850Y8583882</ExchangeId>
      <Price>
        <Amount>625</Amount>
        <CurrencyCode>USD</CurrencyCode>
        <FormattedPrice>$6.25</FormattedPrice>
      </Price>
      <Availability>Usually ships in 1-2 business days
      </Availability>
    </OfferListing>
  </Offer>
</Item>

This response shows how the OfferListingId element is a child of the Item element.

The Availability element in the preceding example is not a reliable means of determining whether or not an item is truly available for purchase. Its message concerns how quickly an item can ship when it is in stock. A value returned for Availability does not guarantee that the item is in stock.

	Tip
	The next chapter talks about adding items to a customer's shopping cart. While it is possible to add an item to a cart using an ASIN, the preferred means of adding an item is by specifying an OfferListingId because an OfferListingId, not an ASIN, guarantees that an item can be purchased.