I'm trying to automate the addition to and management of our products on Amazon. Looking at the API documentation for the MWS API it doesn't look like there's a way to determine if a product has already been added to Amazon by another seller and if so what its attributes are.
We are building a new product database for all the products we sell and have a table specifically for Amazon attribute data fields (ASIN, etc.). If Product information is already on Amazon, we'd like to pull that data via API and store it to our own database as well.
If you attempt to add a product via CSV and that product already exists on Amazon (and your attributes are in any way different ("m" != "medium") you'll receive and error. In that case you can just piggy back that existing product information and just upload a CSV with your price and quantity for a particular ASIN/SKU/UPC. We'd like to do away with uploading CSV files and again, have our own product table for Amazon attributes.
Will I need to also leverage Amazon's Product Advertising API to determine this or can it be done via MWS?
The documentation for Amazon's APIs aren't exactly fantastic and it's been slow going trying to sort through it all.
Additional information: We're working with Ruby.
Amazon's Merchant Web Services API is limited to your Merchant account. So the answer to your question is that yes you will need to use Amazon's Product Advertising API to get information about products that aren't already listed.
That being said you should be aware that there are new restrictions being placed on the Product Advertising API that will limit the number of calls that you can make on a daily basis to 2,000. In addition to this you will have to get an Associate ID that will be tied to your account and needs to be sent with any request.
Also, I find that the information collected using the Product Advertising API is sometimes out of sync with the site and have resorted to scraping the info from the site itself. This has more overhead but you can be assured that the data is current. Of course this is only useful if you already have an ASIN or are dealing strictly with books (which use the ISBN as an ASIN) or Music CDs (which I believe use the UPC as an ASIN).