Probably simpler as: Whenever a source deals damage to Undercity Scoundrel, that source's controller puts twice that many cards from the top of his or her library into his or her graveyard.You /might/ be able to reword Espionage as just: (This creature deals damage to players in the form of putting twice that many cards from the top of that player's library into their graveyard)Simpler?
The wording seems somehow clunkier with "in the form of" in there. I made it targeted because I want interactions with other cards you control. See Unwavering Plague, today's bonus card.
"This creature deals damage to players in the form of putting twice that many cards from the top of that player's library into their graveyard"Would be better worded as "When this creature deals damage to a player, that player puts that many cards from their library into their graveyard instead."Or whatever the common parlance for replacement effects and milling mechanics are these days.
Or, pretty much as it is. I think those are the common wordings.