Why a Skill is still not enough
A clear workflow can still drift; harnesses add checks, evals, and fallback behavior.
A Skill answers “how should this run?”
It can define the workflow clearly, but it does not guarantee stable execution.
A harness answers “how do we know it stayed on track?”
You still need to define:
- which inputs must keep passing over time
- which failures happen most often
- whether failure should retry, degrade, or hand off to a person
Common trap
“My prompt and Skill are detailed, so the system should be stable.”
In reality, models, context, data, and tool behavior all change.
So what is a harness?
Think of it as the checking, evaluation, and fallback layer around a Skill.