It actually is detailed in the summoning section.
Summoning
A summoning spell instantly brings a creature or object to a place you designate. When the spell ends or is dispelled, a summoned creature is instantly sent back to where it came from, but a summoned object is not sent back unless the spell description specifically indicates this. A summoned creature also goes away if it is killed or if its hit points drop to 0 or lower. It is not really dead. It takes 24 hours for the creature to reform, during which time it can’t be summoned again.
But as I pointed out that's not the case because a calling spell is being used, then that was refutted by saying it was an inherent thing of outsiders. I flatly said no to that.