Most people seem to mean "Skills don't pollute the context window [with their entire contents]", they just elide the part in brackets.

There is no magic and people should be more precise when discussing skills.

Yes, but I expect that the elided part is less important than people assume it is.

Token count is a less important factor in context pollution than idea count. The worst of the rot factors are when models latch onto irrelevant information, or over-index on some vague idea/suggestion as if it was a hard direction, and then go off course.

The names + one-line descriptions of 10 tools can do as much (or more!) to distract the focus and intentionality of an agent than a 30k token exhaustive API documentation of some tool.