How can I get the (randomly generated) watcher ID?

I'm creating a watch in Kibana, and Elastic creates its ID as a random hash. That's fine as I don't necessarily want to override it.
Now in the watcher JSON definition, I'm trying to get the randomly generated watcher ID to no avail.
I'm trying ctx.watch_id, but what I get is "_inlined_".
Is there a way that I can get the actual randomly generated watcher ID (e.g "jei334j-kjlw883-lkjeilww-kkeee")?