Google Actions Smarthome Oauth role confusion

Question

I am studying the smarthome program belongs to Actions on Google(Official Overview)

Figure 1

In the figure, google said that it need oauth2 authentication, but I have a question about what's the role of "Assistant Client App" in this oauth2 authentication procedure, is "Assistant Client App" the Third-party application so called in the OAuth2 model or other role?

Another question is that if the "Assistant Client App" is the Third-party application, does it mean that I have to build a Oauth server so the "Assistant Client App" can come and ask for the access grant?

Thank You for help!!!

Answer 1

The Assistant Client app is the application on one's phone for the Google Assistant. In the settings one is able to set up a link to a smart home integration.