Currently the Rachio integration uses several webhooks but doesn’t subscribe to all them all. In particular the Weather Intelligence webhooks (Skip, Climate Skip, and Freeze) could be useful within HA for other purposes. For instance, I have on Rachio and two other non-smart irrigation controllers. If I had access to the Weather Skip information from my Rachio, I could hook up a relay on the other controllers and utilize an automation to make them semi-smart by hooking them to the same Weather Intelligence skip value. I also have a roll-up shade on one window. If I could get information on a Wind Skip event, I could choose to not roll down the shade due to high winds.
The API is here (though much of it is already implemented in the Rachio integration)
The existing Rachio integration: