What data can be retrieved via API depends on:
Which controls are in the software in Connext or Compact CC
Which sensors are connected to the Connext or Compact CC installation
The software version of the Connext or Compact CC.
In short, the datapoints which are available to visualize in the charts of Operator are also available via API.
An overview of the standard historized data points is included in the download, available in English and Dutch.