I have a Homematic CCU2 with a HM-TC-IT-WM-W-EU thermostat. Using the Google Assistant binding, I configured the thermostat group as follows:
Semantic Class: RadiotorControl
Metadata: Google Assistant:
Thermostat
Thermostat modes: on=Auto mode:Manu mode:Holiday mode
Thermostat temperature range: 17,24
Items:
Temperature
Metadata: Google Assistant: thermostatTemperatureAmbient
Set Temperature
Semantic Class: Setpoint
Semantic Property: Temperature
Metadata
Google Assistant: thermostatTemperatureSetpoint
Control Mode
Semantic Class: Point (should may be "Control"?)
Metdata:
Google Assistant: thermostatMode
However, in Google Home only presents the thermostat as read-only, i.e., there is no slider:
I had to create an extra item with humidity as integer. The Homematic devices returns it as float, but Google Assistants expects an integer in the range 0-100
I am not sure of the mode setting when it comes to Homematic thermostats. They have three modes: “Auto mode”, “Manu mode”, “Holiday mode”, which can not be really mapped to the modes Google’s API expects: Cloud-to-cloud | Google Home Developers They also have additional boolean-like modes like “Comfort Mode” and “Lowering Mode”.