Add description, format and unit of the parameter in the API

**Is your feature request related to a problem? Please describe.**
#31 shows that it could be appreciated to have a description of the current API with at least units.

**Describe the solution you'd like**
Could be documentation in code, wiki or external documentation.

**Describe alternatives you've considered**
N/A

**Additional context**
Easy for beginners of hacktoberfest.
