Cool determines your resilience, composure and effectiveness in operating from stealth. Each level of Cool will:
|Increase Crit Damage by 2%.|
|Increase all Resistance by 1%.|
|Increase stealth damage by 10%.|
|Reduce the speed at which enemies detect you by 0.5%.|
|Increase monowire damage by 3.|
Your Cool attribute also determines the maximum level your Stealth and Cold Blood skills can reach.
Like Technical Ability, Cool suffers from the fact that its constituent skills - Stealth and Cold Blood - don’t really require you to actually invest much to make use of, or just aren’t worth investing in at all. This is especially true of Stealth, which contains perks that increase a variety of stealth-related parameters: various forms of stealth damage, detection time, movement speed, poison damage and knife throwing being the broadest themes. While there’s some useful stuff there, a lot of it (Crit Chance while sneaking, damage with silenced weapons while sneaking, headshot damage from outside of combat and damage to human enemies, to name a few) are found early in the tree, and generally a good Overture revolver can come with enough headshot damage, Crit Chance and Crit Damage to one-shot most foes. Just attach a silencer and you’ve got a highly functional stealth build, especially when combined with a potent quickhacking attack. Cold Blood is more fundamentally flawed, as it’s largely built around activating the eponymous buff by killing enemies, but the benefits from doing so are dubious for the number of attribute points it demands, to say nothing of the perk point investment to get the Cold Blood buff stacking high enough and lasting long enough to bother with.
Cyberware that requires Cool to install are also something of a mixed bag, including Shock-N-Awe (chance to release an electroshock when damaged), Catarsesist (increases Resistances), Pain Editor (flat damage reduction), not to mention various lower-quality mods that modify the effects debuffs have on you. To be fair, they’re not terrible, but if the perks on offer don’t appeal to you, the cyberware probably won’t be enough to change your mind.
Cool ostensibly affects your competence at sneaking, and some of the perks on offer will make your life easier, but many of them don’t require much investment, and properly equipped, your protagonist will do well in stealth regardless of your Cool. As for Cold Blood, the various short-term stacking benefits it gives - grudgingly, and only after significant expenditure of attribute point and perk points - are of dubious value compared to what similar investments will get you in other trees.