Even as a tech person, "local API" is not 100% clear to me. Legal persons probably will have a very hard time understanding it.
Some ideas to expand it (probably missing a lot):
all features of the device, which do not require network connectivity from a technical perspective, must be available locally
those features must be accessible through an application programming interface (API)
"available locally" means the functionality must be exposed over network (e.g. WiFi or ethernet), Bluetooth/ZigBee or any other common home automation interface
"available locally" implies that the functionality must work without any connection to the internet in any way
the functionality must be accessible without additional fees
Even as a tech person, "local API" is not 100% clear to me. Legal persons probably will have a very hard time understanding it.
Some ideas to expand it (probably missing a lot):