To see the API calls, you need to set the binding log level to TRACE and check the “Api response” logs.
For users with an Amazon Echo it might be an option to use the Echo Binding and control the heating via the Echo. But I did not test this yet on my own.
I wonder if tado also restricts these API calls which come from the tado Alexa Skill. They most likely cannot distinguish between real Alexa voice commands or commands coming from the Echo binding via the heating things.
Or one could also just fake a voice command instead of using the heating thing from the Echo binding
You can calculate the basic daily count from your number of devices N as (24 x 60 x 60 x N / refreshInterval) (assuming that all devices have the same refreshInterval).
The number N includes all Tado controller devices and your geofencing mobile phones.
On top of the basic daily call count will be:
one per hour for each battery device.
one for every control action issued by OH (based on a rule of something..)