So the following situation came up in a recent session: A party of PCs (built at chest deep) ran into some out of control red court vampires (in horrible bat-monster form, no flesh masks). Our wizard decided to create a magical block against them, then the player said, "Hey, I'll make it a spirit block, making my pentagram (a holy symbol to my character) shine with bright light, to take advantage of the vampire's vulnerability to sunlight and holy stuff. Wait, does my character even know about that weakness? Do I need to roll lore first?"
We just hand waved it, and it turned out not to matter in that combat, but it got me thinking about catches and lore checks in combat. It seems like that should be one of a Wizard's best tricks in combat against magical creatures. "That's may not look like a fey, but it is. Hit it with cold iron." "That's a rare blue-bellied soul-sucker. It's only vulnerable to obsidian." But does a character with high lore need to spend an exchange to see if he knows, or can deduce, a monster's catch? It's not quite the same as assessing or declaring an aspect, and it has a different in-game effect.
Should a character with lore get a "free" lore check to see if he knows a monster's catch? Should it always take a complete exchange? Maybe a suplemental action?
How do you estimate the difficulty of the roll? I assume it's different for a catch that's worth +0, +1, or +2 for obscurity of the information. Should the monster's social skills be taken into account?
I'm not worried that this is going to break my game, but I'd love to hear what other folks are doing in their games, and how it's working out for them.