Hey @ripci - the best way to do this would be to set up a webhook subscription for your app to the checkouts/create or checkouts/update topics, if you haven’t looked at this as an option yet. This would trigger Shopify to send out checkout-related data when the checkout is created (include the checkout ID/URL) in JSON format. Let us know if you have any other questions and we’d be happy to answer on our end. Hope this helps!
Al | Shopify Developer Support