Item › Pokémon Tool
Prevent all effects of your opponent’s Abilities done to the Pokémon this card is attached to. Remove any such existing effects.
· Pokémon Tool rule: Attach a Pokémon Tool to 1 of your Pokémon that doesn’t already have a Pokémon Tool attached to it.
illus. Ryo Ueda
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May I know is this effect will prevent hoopa ability?
I don’t believe this card allows you to ignore SLG Hoopa’s Ability. Hoopa’s ability is an effect on itself, while Stealthy Hood specifies effects of your opponent’s abilities done to the Pokémon this card is attached to.