What is the difference between the two fields ExternalProductID and ProductListingDetails ? When should I use each of the fields when listing / revising items?
These fields help you list your item an eBay Catalog product. The advantage of using these fields is that it helps you pre-fill item information, like the standard attributes, description and picture. You can only use one of the fields in your request.
Here is an overview of the two fields:
ExternalProductID: can take in a ISBN, UPC or EAN (for Books Media Movies Games), keywords for Tickets and eBay ProductIDs (memento strings).
If you choose to use ExternalProductID:
You do not need to know the eBay ProductID
It automatically populates the description, attributes and photo - the user does not have an option to not use it.
It si supported only in AddItem.
ProductListingDetails: takes only the eBay ProductID.
If you choose to use ProductListingDetails:
You have the option of using eBay's product description, attributes and photo.
It is supported in AddItem, RelistItem and ReviseItem.
Here are some use cases that will help understand when to use the fields:
Case1: Listing an eBay Catalog item in BMMG categories
You can take the short cut of using ExternalProductID (no need to find the eBay ProductID)
If you want to list with your own picture then find the eBay productID and use ProductListingDetails
Case2: Listing an eBay Catalog item in non BMMG categories
Find the eBay ProductID and use ProductListingDetails.
Case3: Item listed without any product details and need to add the product information
Find the eBay ProductID and make a ReviseItem call with ProductListingDetails *
or end the item and make an AddItem call with ExternalProductID if listing in BMMG or ProductListingDetails if listing in non BMMG categories
Case4: Item that was listed without any product details has ended
Find the eBay ProductID and make a ReListItem call with ProductListingDetails *
Make an AddItem call with ExternalProductID if listing in BMMG or ProductListingDetails if listing in non BMMG categories