I have a friend who uses Siri to great effect. Sometimes I use voice typing. I have decided a few times that Android's Google Assistant is mature enough for me

I have a friend who uses Siri to great effect. Sometimes I use voice typing. I have decided a few times that Android's Google Assistant is mature enough for me to try it out. But for two fatal flaws: it can't do anything useful, and I don't know how to speak to it. The Assistant can't arbitrarily control other apps on a program, for instance if I want to say "log into my bank and check my balance on checking" there's no interface for that. We're left with mundane crap like "set an alarm at 10am." Furthermore, I don't know the vocabulary of my Assistant. To be understood properly on the CLI, I've learned how to speak to Infocom's z-Machine, the Bourne shell, Cisco routers, hell I'm a full-fledged Protocol Droid at this point. But I have no idea what to say after "OK, Google!"