Ooh great call Brett. UUID is indeed available in Retool!
You invoke it like:
{{ uuid.v2() }}
or {{ uuid.v4() }}
There are also a couple workarounds listed in these posts in case they're helpful for you:
http://community.retool.com/t/auto-increment-on-row-id-google-sheet/9387/6
Let me know if you have any questions about them!