Similar to how the Data Cloud integrations provide ETL_MODIFIED_DATETIME (a timestamp of the date and time the data was modified), it would be really helpful for each call record to also include a similar field in API responses.
This would be useful for seeing which historical records are due for a resync after something has been updated (eg transcript updated based on custom dictionary words, speakers identified via the UI, the call was associated to an account in the UI, etc).