Documentation for nullable fields in Event Types in the Events API?

Hi Folks,

I am currently writing some integrations with the Events API. One thing that I’m not clear on is what types are nullable. For example, in the first CreateEvent for a repository the ref in the CreateEvent's payload will be null. Another example, the description field in a CreateEvent can be null if unset, instead of the empty string.

Is this documented anywhere? It does not seem to be mentioned here https://docs.github.com/en/free-pro-team@latest/developers/webhooks-and-events/github-event-types and it also doesn’t seem to be mentioned in the API spec https://github.com/github/rest-api-description/tree/main/descriptions/api.github.com - the spec does not look like it contains payload types yet, but I may have overlooked it.

Thanks!