Kairos has all features available for free with limited usage (throttled at 25 API transactions /minute & capped 1,500 /day).
This is a version 2 of the API documentation. See more information on Kairos Documentation Site: https://www.kairos.com/docs/api/
This is a Kairos API Wrapper with 11 available features:
You can see how to configure Kairos account here.