You have learned how to use your agility to greater purpose in battle.
Prerequisites: Weapon Finesse
Benefit: You may add your Dexterity modifier in place of your Strength modifier when wielding a light weapon or a weapon that gains the benefits of the Weapon Finesse feat (such as the rapier) when determining additional damage inflicted upon a successful attack.
(Editor's Note: The PoW errata had the following as a note on the changes to Deadly Agility: "When wielding a weapon in your off-hand, Deadly Agility will add the same fraction of Dexterity as you normally would for Strength.")