To understand what the Mouth Tool adds to the game, it would help to briefly review the other tools.
Massager: Speeds up massaging, or can be used for large boosts in Arousal.
Penis: At high Arousal and later days, greatly increases Arousal... & decorates client with cum.
Mouth tool: Slightly increased Arousal & decreased Fear vs Hands when sucking or licking.
Every short click causes a small, quick kiss on the body.
No battery or limit, unlike the Massager.
+
Kissing Minigame: High risk, high reward way to sharply increase Arousal,
OR, safely return to a higher Arousal point.
Uniquely, it reduces Fear for every point of Arousal it produces.
Success chance sharply increases if the Client was kept at higher Arousal states for a while.
Limited by cooldowns that decrease Success chance.
(Activate Kissing Minigame by left clicking the face area with Mouth Tool active.)
The Mouth tool/Kissing will be helpful for the Early Game, and fun for the Late Game.
Kissing also acts as a comeback mechanic when you accidentally increase Fear a bunch