Boundary
The procedure becomes its own artifact. The model or host can follow it without reading the implementation.
What this adds
Capture usage as a checked-in procedure.
A tool only tells you what it can do. A skill or procedure tells you when to use it, what inputs matter, how to validate the result, and how to recover when the first attempt fails.
This moves the intelligence from hidden habits into a reusable file another person or host can follow.
Done when
Another person can use the file to get the same result and can see the validation rules without opening source code.
Real-world analog
Make files and similar checked-in procedures occupy the same role in non-AI stacks: they capture the repeatable recipe around the underlying commands.
Why this matters
This is one of the clearest ways to understand the distinction between a raw tool and a higher-level capability.