The restock inventory recommendation report is much more helpful when the (seller) warehouse inventory level is supplied, but this obviously changes often is is way too difficult to keep updated by hand if a seller has more than a few listings. I cannot find a way to update it through the MWS API. Am I missing something? Is there an undocumented way to do this? If not then this is a request. The recommendation system took a lot of Amazon development effort and it seems like not being able to keep this field populated efficiently hamstrings its value to larger sellers.
What exactly are you trying to update through the MWS API?