Edward's power is the ability to detect falsehoods. This includes anything of text, verbal, or image; the catch is that said falsehood has to be communicated to him. It's pretty straightforward: if something doesn't jive with reality, he will know. He's pretty much a harbinger of absolute truth.

Also: he has a tendency to mutter "falsehood" when he detects one. Some characters may or may not pick up on that.

TWO QUESTIONS:

I. That ace with you?

II. If you can warp the very fabric of reality on a Scarlet Witch scale or if you are a shapeshifter MENTION IT TO ME. I decided those are loopholes.