square.onInventoryCountUpdated subscribes to inventory.count.updated for the selected seller. It requires INVENTORY_READ.
Example
automations/square-on-inventory-count-updated.automation.ts
Event
The quantity was updated for a catalog item variation. Webhook notification data is packaged as InventoryCount[] . The signal resolves to the officialSquare.InventoryCountUpdatedEvent payload with type narrowed to inventory.count.updated.