We have been doing eBay API development since 2006. We are Trading API experts. Adding items to eBay can be very complicated. There are many rules and limitations. We work directly with the eBay Support Team to help solve any problems that may arise.
We have done solutions using Finding API and Shopping API also.
We helped SellerSourcebook to add Business Policy support for their users. This significantly reduced the effort required to add items.
Platform Notifications can be provide you with very important information that can make all the difference to your sellers. However, they can be tricky to implement. And we have a lot of experience in dealing with the many subtle differences in the data coming from eBay.