I have spent the past month reading skill libraries, and I kept feeling like I was comparing things that would not line up. One guide would compress six books on legacy code into an ordered playbook. Another would define a seven-phase chain where each phase writes an artifact and refuses to advance until a gate passes. Both are called skills. Both are instruction files you drop into a repo. And they are not doing the same job at all.
The word hides the split. Once I saw it I could not unsee it, and it explains most of the ways these setups fail.
Two dials, not two bins
The clean way to say it is that a skill can carry two different things, and they are independent dials rather than a pair of boxes.
Content is knowledge packed into steps. It tells the agent what to do, in the right order, distilled from someone who knows the domain. The Wondel guides are a clear example. Their legacy-code playbook (checked 2026-07-17) compresses canon like Feathers' Working Effectively with Legacy Code, Fowler's Refactoring, and Ousterhout's A Philosophy of Software Design into a sequence: characterization tests first, then readability, then restructure, then scale. The value is that you carry a shelf of canon in your pocket. The content tells you the move.
