You'd think the Nest x Yale Lock would support Google Assistant from the outset given its pedigree, but not so -- you've had to use the app. It's finally here, though. As of August 29th, you can use Google Assistant to control the Nest x Yale Lock with your voice. You can lock the door or check its status whether or not you're at home, including as part of Assistant's Routines. If you're ready to pack it in for the night, you can lock the door as you're shutting off the lights.
The feature works on both smartphones as well as Assistant-equipped smart speakers like the Google Home series. There's no mention of unlocking (probably for the best given the security risks), but this might be ideal if you'd rather not pull out your phone just to be sure the door really is locked.