Unfortunately, zap receipts can be spoofed so they're probably not good to use for wot.  The only one that knows for sure if a zap was real, is the recipient that manages the wallet that received the zap.

"This isn't really a payment proof, there is no real way to prove that the invoice is real or has been paid. You are trusting the author of the zap receipt for the legitimacy of the payment." From https://github.com/nostr-protocol/nips/blob/master/57.md