When a Booking Engine wishes to work with the BookingCenter APIs to Query Rates & Availability and Save Bookings, they usually use the following APIs:

1) Connect to the ‘PMS/CRS’ and retrieve hotel rates and availability, with specifics for finding which rates are Packages, what Items they include, and Quantity and Price.  To learn about rates and availabiity for an XML developer, we recommend reviewing the KnowledgeBase articles here.

OTA_ HotelAvailRQ/RS-

From: https://docs.bookingcenter.com/display/MYPMS/APIs+and+Web+Services+Available+From+BookingCenter would provide an array with Type and Rate availability, and you could parse that to get the ‘lowest’ available rate. You will have the credentials (User ID and password) stored for the Rates and Avail calls you make for BookingCenter customers, so you can use those credentials to enable this API call to return what is needed.  

2) Save the Booking, what we call the NewBooking message

OTA_HotelRes

As we explain at: https://support.bookingcenter.com/index.php?/Knowledgebase/Article/View/667 when you are focusing on querying and selling Packages, understanding the way you call for Inventory Items (which constitute the ‘parts’ of a package) and then saving them with a booking is critical. 

If the BookingCenter customer is using a Payment Gateway, then you can request the server 'process' the deposit amount as part of saving the Booking.  If we get an authorization, then the server sends back the Booking ID (reference number) and you can be assured the 'payment' was stored and saved with the Booking. See: Point of Sale/MyCard (credit cards, hardware, etc.) part of the XML KnowledgeBase to get teh settings accurate and understand errors, especially with failed deposits.