I'm looking to add [RentalCarReservation] (https://schema.org/RentalCarReservation) to the consumer-side confirmation emails sent for a large, multinational rental agency but am running into two key questions:
Is there a corresponding Google Now tag that will correctly handle and parse vehicle rentals in particular at this time, or should we use a more generic order markup scheme until such time as there is support for this? It should be noted that none of our competitors seem to be using microdata at all, so there's no industry trend.
As asked earlier on this tag, what is the state of JSON-LD adoption for Google Now tags? By its nature the RentalCarReservation schema requires JSON rather than RDFa or similar.
RentalCarReservation is currently supported by Gmail markup, you can find more info and JSON/microdata examples here:
https://developers.google.com/gmail/markup/reference/rental-car#basic_reservation_confirmation
JSON is supported, as stated in the following link:
https://developers.google.com/gmail/markup/reference/formats/json-ld
In order to be enabled to send RentalCarReservation to your Gmail customers, you will have to register and provide a sample email, more info here:
https://developers.google.com/gmail/markup/registering-with-google?hl=en