Amazon MWS API: Reliably Detect A Marketplace Offer vs. A Primary Product Listing?

Question

Is there an MWS or AWS API call that I can make using a product ASIN that will tell me whether or not the information being returned from the Amazon servers is coming from the main product listing or from one of the "additional sellers" that are piggybacking off of the main product listing?

What I'm trying to do is programmatically determine if the MerchantId I'm using in the GetMatchingProductForId() call is the same MerchantId that originally created the product listing on Amazon. If they aren't the same it means (in theory, anyway) that I can work with a much smaller subset of the data, and post just the information that's required for the "Condition" and "Condition Note" values in a Marketplace Offering.

And yes, this question is directly related to How to get Seller Name from Amazon in ItemSearch using amazon API, but the API call and parameters in the answer have been deprecated by Amazon. Literally, the request returns <MerchantId>Deprecated</MerchantId> in the response, so I can't compare the Merchant ID value that I'm using to make the call against the <MerchantId> node returned in the response.

Answer 1

After a lot of (very tedious) research and experimentation I've settled on a series of three MWS API calls to determine whether a product is an Amazon Marketplace Listing or an Amazon Marketplace Offering.

GetCompetitivePricingForSKU -- This call returns an XML CompetitivePrice node containing a belongsToRequester attribute set to "true" or "false". The caveat (and the reason why I'm using three different MWS API calls) is this call fails miserably for merchants that have predetermined shipping charges for their products.

GetMyPriceForSKU -- This call will return an error if the merchant doesn't "own" the Marketplace Listing. Purely anecdotal and empirical, though.

GetMyPriceForASIN -- The least reliable call of these three. Sometimes it will return an XML MerchantSKU node... and sometimes it won't.

Since Amazon doesn't provide any definitive answer (or documentation) for this issue, please take all of this advice with a large grain of salt. Run your own use-cases and see which one(s) work for you.

Answer 2

The GetProductForID is intended to give you details about a product. Mainly this is used to get the ASIN by using a UPC code, and other product details such as bullets, image, size, etc.

If you are trying to see if your offer for the same product is competitive you can either use the GetLowestOfferListingForASIN (to get the asin use the GetProductForID (if you have some sort of id like UPC) or ListMatchingProducts to do a text search). That way you will know what type of offer you need to place to try and get the buy box.

If you are looking to get more details to all the unique offers listed for a product (new, used, etc), then you need to use the subscriptions API (its pretty new). This can get pretty complicated.