I need access to an API key. If I keep a credit card on file, do I only get charged for the calls I make with the API or is there any other fees I need to know about before putting a credit card on file?
It’s pay-per-use only. No base fee. See Pricing page and FAQ at bottom for details.
Do you get charged for the prompt as well as the response?
Yes, see pricing page. Some models have different rate for Prompt vs Completion (response)