C# – Amazon Marketplace API

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).

In order to use Amazon Marketplace Webservices (MWS) you will need a Pro Merchant seller account, an Amazon WebStore account, a Checkout by Amazon account, or an Amazon Product Ads account. The Pro Merchant or Professional Sellers account is currently priced at £25.00 or $39.99 USD per month. Then sign up for MWS by clicking the Sign up for MWS button at http://developer.amazonservices.co.uk/ (or appropriate for your region).

It is my understanding that by calling Amazon Seller Service you can get a "sandboxed" MWS account, although I've never used that.

Once that's set up, you have two options:

1. Create a tab delimited text feed with your product information (called "flat file" in the documentation)
2. Create multiple XML feeds (mostly these four: products, prices, inventory and images)

Once that's done, you use the following API calls:

1. SubmitFeed to send your data to Amazon and put it in the processing queue (you will need to call this multiple times if using the XML formats)
2. GetFeedSubmissionList to see if it was processed
3. GetFeedSubmissionResult to see if anything went wrong

If done right, using above APIs can completely automate the process of creating new products on Amazon, linking your data to existing products (by linking to the same ASINs, EANs, UPCs or ISBNs) as well as changing images, prices and inventory.

The Amazon Developer site has C# sample client code for you to play with. Other useful references:

• Amazon Marketplace Web Service Feeds API Section Reference
• Selling on Amazon Guide to XML