For the AddItem family of calls:
Contains the name and value(s) for an Item Specific. Only required when the ItemSpecifics container is specified. For the AddFixedPriceItem family of calls:
The same NameValueList schema is used for the ItemSpecifics node, the VariationSpecifics node, and the VariationSpecifcsSet node.
If the listing has varations, any name that you use in the VariationSpecifics and VariationSpecificsSet nodes can't be used in the ItemSpecifics node.
When you list with Item Variations:
a) Specify shared Item Specifics (e.g., Brand) in the ItemSpecifics node.
b) Specify up to five VariationSpecifics in each Variation node.
c) Specify all applicable names with all their supported values in the VariationSpecificSet node.
See the Variation sample in the AddFixedPriceItem call reference for examples. For PlaceOffer:
Required if the item being purchased includes Item Variations.
For more details, see Requiring Product Identifiers Mandate