Can the hotel booking API send a special request to the hotel, like a late check in or a room on a high floor?

Yes, in most cases you can send a special request with a hotel booking through the API, but it is worth knowing that it stays a request and never becomes a promise. When you make the booking you can usually pass a short note along with the guest details, asking for something like a late check in, a room on a high floor, twin beds instead of a double, or a quiet room away from the lift.

That note travels from your booking to the supplier, and the supplier passes it on to the hotel. How much of it survives the journey depends on the supplier you are booking through. Some accept a free text note of a reasonable length, some only accept a short list of standard preferences that they have codes for, and a few strip out anything they do not recognise. Most suppliers expect the note in plain English, so writing it in another language is usually a waste.

The hotel makes the final decision, and it makes it when your customer arrives, not when you book. A high floor or adjoining rooms are given only if the hotel has them free that day. Requests that cost the hotel money, such as an extra bed or an early check in, are usually treated as a chargeable extra and settled at the property. Anything that really matters, like a wheelchair accessible room, is safer to confirm with the hotel directly as well.

Before you rely on this, ask your supplier which request fields they support and how long the text can be, then make one test booking and check the note appears on the confirmation you get back. Tell your customer it has been requested and not confirmed, so nobody is disappointed at the desk.