Love this! I made a similar IR controlled "API" to toggle my in-window air conditioner on/off last summer.
Btw, I don't think the Google Home can actually control Chromecast. They advertise it but each time I've tried stuff like "Okay Google, mute my TV" or "Okay Google, turn off Chromecast" it's said something along the lines of "Sorry, I can't do that yet, but I'm getting better every day". I switched off the Google Home after 2 weeks back for the Echo, so maybe it's gotten better.
Btw, I don't think the Google Home can actually control Chromecast. They advertise it but each time I've tried stuff like "Okay Google, mute my TV" or "Okay Google, turn off Chromecast" it's said something along the lines of "Sorry, I can't do that yet, but I'm getting better every day". I switched off the Google Home after 2 weeks back for the Echo, so maybe it's gotten better.