Amazon’s Product Advertising API functionality will be partially changed on October 26, 2011.

・AssociateTag will become a required parameter for all API requests and will be subject to verification during request processing.

・The SellerLookup, SellerListingLookup, and SellerListingSearch operations will no longer be supported by the API.

・The ItemPage parameter returned as a result of ItemSearch requests will be limited to a maximum of 10 pages.

・The MerchantId parameter will no longer be supported as a filtering element for offers, variations, and search results.

・Data returned in the Offers and ItemAttributes response groups will be limited to the most frequently used attributes.

More details are written on the following page:

・Product Advertising API

Amazon’s API is famous for making developers cry with frequent specification changes, but personally, the inability to use MerchantId is painful.

That’s all from the Gemba.