[orochimaaru]

Please don’t charge per call. It’s irritating. Charge for a block of calls or better still a block of calls in a moving time window. This way prospective clients don’t have to go ahead and estimate their entire design before using your product. A block (eg 100k calls every 24 hrs) gives them an easy way of balloarking their costs as well.

[soco]

And segmenting the users: no API access needed no extra cost, low API calls needed (still free tier but with limited quota - useful for you to know and to talk to them) and the big users with said block of prepaid calls (pass them through the free API tier first with a grace period).

[buffet_overflow]

If OP takes this approach, please please please make this usage data easily accessible, ideally both as a (free?) API endpoint and as a timechart/table in the web UI if applicable.