Nah, I think it should be assumed that any creature summoned will be hostile to the summoner unless otherwise controlled. That's pretty standard for any system or mythos, after all, and for good reason.
I dunno; I would agree for things like fiends, efreets, and elementals, but not a troll, or even moreso, a starving crocodile, from the wilds nearby.
A magical being summoned from another plane is likely to be able to detect the magics used to summon it and discern their source. A mundane creature summoned from within this plane—especially a nonsentient one—is much more likely to just be confused and attack everything around it.
