We do quit a bit of data lookups. Ex, we support over 1000 manufacturers and we're constantly referring customers to mfg's. With a JSON call, we could hit "/" like for messages but fire a lookup for a given manufacturer to call our own API endpoint to return mfg name/website/address/phone.

Another use case, we're constantly providing tracking... we could create an endpoint to return all tracking associated with an order.

Or, same to lookup all order ID's assoc with a customer ID.

We see lots of use cases.