AI Guides › Skills & Agents
The One-Rule Pattern: Why Every Good Skill States Its Point First
By Nigel Guy · 2 min read
Most skill documents open with context — background on the tool, a description of the general area, a paragraph of throat-clearing before anything useful. By the time the actual instruction shows up, you've read past it once already, half-attending, because nothing signalled "this is the important sentence."
The rule: a skill should state its point in one or two sentences before it states anything else — if you can't compress what the skill does into a single sentence, you don't yet understand the skill well enough to write it.
The mechanism
- Write the rule sentence last, put it first. Draft the whole skill, then go back and write the one or two sentences that summarise what it's actually for. This order works better than trying to state the rule before you've worked out what the skill does.
- Make it a rule, not a description. "This skill helps with scheduling" is a description. "Never book a meeting without checking for an existing hold on that slot" is a rule. The difference is that a rule tells you what to do when the situation is ambiguous; a description just tells you the topic.
- Bold it, and put nothing above it but the title. No warm-up paragraph, no "in this document we will…". The rule is the first thing a reader — human or the assistant executing the skill — actually needs.
- Test it by covering the rest of the document. If someone reads only the bolded rule and nothing else, do they know roughly what to expect from the skill and what its limits are? If not, the rule is still too vague or too broad.
- Let everything below the rule unpack it, not repeat it. The steps, checklist, or table that follows should be the mechanism that makes the rule actionable — not a restatement of the same sentence in longer form.
What to skip
Skip writing a rule that's really a mission statement — "empower better decisions through structured automation" states nothing a reader can act on. And skip stacking multiple rules at the top hoping one of them lands; if the skill genuinely needs several unrelated rules, that's usually a sign it should be split into separate skills, each with its own single point.
Guardrails
- A one-sentence rule is a compression, not a full specification — it orients the reader, it doesn't replace the steps underneath it. Don't skip writing the mechanism just because the rule sounds complete on its own.
- If you find the rule changing every time you edit the skill, that usually means the skill's actual scope hasn't settled yet — finish deciding what the skill does before you polish the sentence that summarises it.
- This pattern is about clarity, not brevity for its own sake. A rule that's short but says nothing specific ("be careful and thorough") has failed the test just as badly as a rule that's three paragraphs long.
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