There is a watcher history index that contains information about all watch executions. You could query that one as part of your watch.
GET .watcher-history-*/_search
{
"size": 1,
"query": {
"bool": {
"filter": [
{
"term": {
"watch_id": "my_watch"
}
}
]
}
},
"sort": [
{
"trigger_event.triggered_time": {
"order": "desc"
}
}
]
}
Hope this helps!
--Alex