I have tried printing a FedEx shipping label and am seeing an error returned:

2039: Incomplete commodity description 1 (COMMODITY_INDEX=1)


If you are getting this error while shipping internationally via FedEx, this means that the description on your shipment’s first customs line item did not meet FedEx’s keyword criteria. For FedEx it's possible to use Commodity Description Item's Extended Property to submit the description of a product, as otherwise the Item Title will be used. The Property Name can be mapped in > Shipping > FedEx Properties.

Please see Table 260 for the list of vague descriptions that do not match the customs requirements:
Web Services Developer Guide Global

Related articles:

Shipping - Adding shipping details to items