For our direct listing to eBay functionality of AccelerList we've made it super easy to take products and list them quickly to eBay.
Each new listing starts with a "search" from the Amazon catalog. Searching eBay for your product via the API would return too many listings as eBay allows for multiple listing of the same product.
So we start with an Amazon search of the product in order to find the right item and then we pull as much of the data over from that Amazon listing as we can in order to help shorten the time it takes to complete the eBay listing.