A skill becomes reliable when it answers three questions clearly: what is the one task it does, what inputs does it need, and what does a good output look like. Skills that try to do too many things or leave outputs loosely defined produce inconsistent results.
The Single-Task Principle
The most common reason a skill produces inconsistent output is that it’s trying to do too much. A skill called “help with my course” is too broad — the agent doesn’t know where to start or when it’s done. A skill called “write a lesson summary from a session transcript” is specific enough to produce consistent, usable output every time.
Think of a skill like a job description for a specialist, not a generalist. A generalist does everything adequately; a specialist does one thing exceptionally. Your best skills will be narrow and deep — covering one task extremely well, rather than many tasks passably.
Inputs and Outputs: The Reliability Checklist
For a skill to work reliably, it needs to specify what information it needs to start (the inputs) and what it should produce when finished (the outputs). A lesson summary skill, for example, needs: a transcript or session notes (input), and should produce: a 300-word summary with key takeaways and one action item for students (output). When both are defined clearly, the agent knows exactly what to do and when it’s done.
Adding one example of a good output — even a short one — dramatically improves consistency. The agent can pattern-match against the example rather than interpreting the instructions from scratch each time. This is especially valuable for educators whose skills need to produce output in a consistent voice and format across multiple runs.
What This Means for Educators
For your teaching business, reliable skills are the ones you can hand off to run without checking every output. That level of reliability comes from specificity, not from more complex instructions. A simple, well-defined skill is more trustworthy than a complex, loosely-defined one. When a skill isn’t working reliably, the fix is almost always to narrow its scope or clarify what “done” looks like.
The Simple Rule
If you can’t complete this sentence in one line, your skill is too broad: “This skill takes [specific input] and produces [specific output].” Write that sentence first, then build the skill instructions around it. That single sentence is your reliability anchor.