[TSoY] Perception in BDtP?

Clinton hasn't defined any perception abilities, because he doesn't believe in withholding information.

That being said, perception abilities per se are not the problem, but rather the ingrained GMing habits they come with. So if somebody wants to use various perception abilities in my games, they're free to do so.

As for guards, my guards tend to have this Ability:

Guarding (Instinct)
The character is an experienced guard, able to keep his attention sharp while filtering extraneous sensory perceptions. The ability can be used to notice dangers and abnormalities, to wait patiently, to make on-the-spot legal judgements, to discern lies related to public security and so on.

Or, as it more commonly appears:

Occupation: Guard (Instinct)
This Ability may be used in checks concerning the occupation in question. The character has experience with the job and it's many contingencies.

The actions used against sneaking are then things like "I scan the hallway lazily while walking by." or "I tap the stones with my spear-but, suspicious." or "I remember the arrangement of twigs on this path from yesterday, it's moved. I look around for animal tracks." and so on. Lots of options.

But really: as far as NPCs are concerned, the above ability descriptions and such are really just rationalisations created on the spot. Any NPC of mine will pretty much be defined by "this is the best Pool, this one's second, this one third" and "this is his highest Ability, it's at X". Then I just set the highest Pool (around 7 for bad-asses, 4 or 2 for lessers) and highest Ability, with the presumption that any other relevant Ability will be at one step lower, and any tertiary Ability at two steps lower. Secondary Pool will be two points lower and tertiary four.

What that means in practice is that I don't even have to know what Abilities my NPCs are using, exactly. I just need to know whether they are within their comfort zone as experts or not, and how competent they are in general. For example, if I had a city guard captain who was Experienced (was that the name for the 2-point Ability?), I'd use Experienced for anything having to do with guard captaining, Competent (1?) for stuff like soldiering and other secondary things and Inexperienced (0) for sailing a boat, say. If I had an UpTenBo Grandmaster, he'd do pretty much anything at Experienced at least; this reflects a balanced player character, those tend to have an Ability for any situation at the time when they're really going Grandmaster.

An example NPC stat block in my style:

A farmer patriarch
Vigor 5 (implying either Instinct or Reason at 3 and the last at 1; haven't chosen between them yet because I don't care)
Master Farmer (implying the ability Farming (V) at Master, with other abilities lower)

If a NPC goes suddenly important, I also add a Secret spontaneously, putting in something relevant to the situation. If, later on, we need to know what other Secrets the character has, I pick more according to taste.

The philosophy here is that you're not really adding anything to the game by figuring out every NPC to the utmost detail. Sure, sometimes you might end up with interesting rules interactions, but for the most part the detail will go to waste. So that's why I only waste time with preparing named NPCs, and even then I usually just jot down the above stuff and a Secret or two. Only if a NPC ends up appearing in several scenes will I go as far as to give him a full array of statistics between sessions. My last campaign had around three NPCs with real stats, I think.