Can I see the price of a hotel room go up or down through the API so I know when to book my customer before it gets more expensive?

Not in the way you might hope. The hotel booking API will show you the current rate when you search, but it does not track price changes over time or predict whether a rate will go up or down in the future. Each time you search for the same hotel and dates, you get today's price, which may be different from yesterday's price. Some suppliers do offer lower rates if you book further ahead, but this depends entirely on the hotel and the supplier you are connected to through the API, not on glideFares itself.

What you can do is search regularly and compare the prices you see on different days. If your customer is flexible about when to book, you could search a few times and show them the trend. However, the API does not have a built-in tool that watches prices and alerts you when they drop, or tells you whether waiting will save money or cost more. The supplier controls the pricing rules, so different hotels behave differently.

Your best approach is to search for the hotel and dates your customer wants, show them today's rate, and explain what you can see about the cancellation policy. If the booking is refundable, your customer can often cancel free of charge and rebook later if the price drops. Check the cancellation terms the hotel booking API returns for each room, as this will tell you whether your customer has that flexibility.