Mouseover the JSON key to see a brief description of each key. Keys that either haven't been identified (or that we haven't gotten around to adding yet) will show 'XXX'. Keys that are light gray are obsolete/legacy but still are returned in API responses.
At certain subscription levels, custom fields can be created allowing you to keep track of whatever data you like. There are several data types available ranging from free text to a drop down. The custom fields are available for use in custom templates as well.
If you spot a mistake or know the purpose of an undescribed key please let us know by emailing kickservapi@veildg.com.