Piratecat said:"The following spells can be cast through a scrying spell: comprehend languages, read magic, tongues, and darkvision. The following spells have a 5% chance per caster level of operating correctly: detect magic, detect chaos, detect evil, detect good, detect law, and message."
Yeah, but I think he meant spells that would work from the scryee to the scryer, not the other direction. I.e. spells that could be used to defend against someone scrying you.
E.g. A scries on B, B notices it, and retaliates with, say, Eyebite.