Hi @pv12 ,
Performing REST API request is not chargeable. You're chargeable for certain action. For example, if in your request you're going to start cluster and run some sql, then you'll be charged standard price for running compute cluster etc.
So to sum up, you can make as many request as you can want and you'll be not charged. But once your request is going to start cluster, rub job (anything involving compute) you're going to pay the price for using that compute