How do I use a smart Inventory to get Windows Hosts?

I’m still new to the Tower interface and I’m having trouble understanding the smart inventory filters

What kind of filter would I need to make to only grab “Windows” machines? I noticed that the “variables” section of each host has a key-pair “platform”: “windows”

Would I just be checking if “variables” contains “platform”: “windows”? It seems really messy…

Never mind, even if I do try that, I get the error:

Invalid query variables__contains=“platform”: “windows”

Is there a better way to filter by OS?