Product manager Igor Slutsker revealed the API’s availability in a blog post, saying that it can be used to support valuable use cases like price drop alerts, back in stock alerts and other important follow-ups that people have requested notifications for.
He provided the following example: “A person is shopping for a shirt, but it’s out of stock. The business asks if they want to be notified when the shirt is back in stock. The user asks to receive a notification, and the business gets a token in exchange. When the item is back in stock, the business uses this token to respond back to the person, letting them know of the item’s availability.”
Slutsker said Facebook will limit the number of one-time notification requests a business can send to a person, and the follow-up will be limited to a single notification.