Supplementary data such as resort fees and other pay local type data, would typically be found in the Errata node of the prebook response.
 
This can vary by supplier, as there isn't 100% support for this amongst all suppliers, but is where you would typically find it if available.
 
Here's an example of a prebook response returned by Expedia

"Errata": [
      "Included: Tax and Service Fee: GBP/27.86 . This charge includes estimated amounts the travel service provider (i.e. hotel, car rental company) pays for their taxes, and/or taxes that we pay, to taxing authorities on your booking (including but not limited to sales, occupancy, and value added tax). This amount may also include any amounts charged to us for resort fees, cleaning fees, and other fees and/or a fee we, the hotel supplier and/or the website you booked on, retain as part of the compensation for our and/or their services, which varies based on factors such as location, the amount, and how you booked. For more details, please see the Terms and Conditions.",
      "Terms and Conditions - link: https://developer.expediapartnersolutions.com/terms/en"
  ]