Answer by Binary Alchemist for Feeds Node processor mapping

Does the Node processor mapping require a unique identifier for the GUID or is this not mandatory?

You do not need to have a unique identifier to import data, but you might get duplicate data if you do not use a unique identifier. From your question I assume you are interacting with the API in the feeds fetcher. Can you get "duplicate" results when using the API? Or, is each import ALWAYS creating new nodes?

Xpath

Use //content/text() to return the json text {"appointmentSet":[{"appts":[]}],"bookingAllowed":false,"maxBookAheadPeriod":25}