Coming back after 3 years to see if there are any plans to add Vendor data, specifically vendor code and cost to the api? As stated, it’s a “very popular” request.
Yes, this is a very popular request and the team is aware. We hope to have more for you soon. 
Two or three years later, and this still isn’t available? Add my name to the list. We can add these through a spreadsheet, but we should be able to do it with an API. As a new user to Square, I’m just digging in and will pile on my frustration as items are unavailable in your API. I need to be able to update the cost of goods when creating items in the catalog and link catalog items to a vendor.
Please add my name to the list. We need this to support showing Unit Cost of items that originate from our supplier manifests. We are using the Catalog API to add/update items to the store along with Inventory API to add stock. We also need to link our products to vendors. With over 10,000 items in the Square catalog, setting those values manually is not possible.
+1 Also very interested in this. Please add my name to the list. Ideally, we would be able to adjust the cost when pushing stock to inventory while receiving a purchase order. A field added to the adjust inventory APIs so include the cost would be great.
@Bryan-Square I am trying to get all vendor information - All vendors for an item, all vendor item codes for each vendor, and cost of goods for each vendor. Is this still not supported?
Is there an easy way to at least pull default vendor, default vendor item code and default item cost?
At this time this is still currently not available with our APIs. We’re constantly working to improve our features based on feedback like this, so I’ll be sure to share your request to the API product team.