I tell the parents a lot I think. Maybe too much.
....both the positives and negatives of the day (if any). They know (at least I hope they do) that it's out of love and the fact that we should work together on xyz behavior.
I usually just indicate the things that are recurring and not that *one* time their kid snatched a toy from someone, kwim? I don't want to be taking trips to the Tattle Turtle either