How to create a Google supplemental API feed
A supplemental feed is to provide additional or more updated data to a Google Shopping primary feed. A rule of thumb is that the item ID in supplemental feed must match the item ID in the primary feed so Google can coordinate the item data.
Data is "supplemented" by feed rules. Basically a feed rule defines how the final data is derived from primary feed and supplemental feed by rules, including priority (e.g. take data from from supplemental feed if available, otherwise use data from primary)
Supplemental feed can be in file or API. File feed can be used to add more data, e.g seasonal promotion ID to the items being sold in Google Shopping. API feed can be used to update fast changing data like stock.
File feed can be created inside the app the same way with primary feeds. However it needs to be manually added into GMC by following steps:
1/ Create supplemental file feed in app.
2/ Select "Schedule fetch" option in the supplemental feed, and provide the file URL from step 1.
API feed require copying the generated supplemental feed ID from GMC into the app feed configuration
Similar to primary API feed, supplemental API feed requires a connected Google Account
The last step is to create a feed rule to utilize the data from supplemental feed. This can be accessed by clicking the corresponding primary feed that data needs to be supplemented, and select "Feed rules" tab
Some example feed rules
- Set availability to "supplemental feed name".availability. If availability has no value yet, take from "primary feed name".
- Set price to "supplemental feed name".price. If price has no value yet, take from "primary feed name".
With these rules, price and availability can be updated instantly by an API supplemental feed when changes happen.