Writing Skills

A skill supplies task-specific knowledge or a reliable operation the model would otherwise have to rediscover. Optimize for correct outcomes, useful evidence, and low overhead. Identical process on every run is useful only where ordering is part of the contract.

Choose the Scope

• Follow the user's requested outcome and existing authorization. A skill does not add approval steps or override repository policy.
• Keep a rule only when it changes a relevant decision or prevents an evidenced failure. Delete generic advice, duplicated rules, obsolete model assumptions, and rhetorical pressure.
• Keep descriptions short: put the concrete task, trigger, and main scope boundary in the first sentence so truncation preserves when to use the skill. Add exclusions only to resolve likely overlap. Avoid firing on every code edit, every test, or every completion when the procedure is only needed for a narrower problem.
• Distinguish shared guidance from repository-specific policy. Edit shared sources first; preserve local variants when synchronizing. Check whole-directory differences before an installer overwrites a skill.

Create or Revise

1. Identify the outcome, owning files, known failure, and existing instructions. Reuse the current conversation's evidence; recollect only missing or stale material.
2. Keep the minimum common contract in SKILL.md; link branch-specific references with a condition and the section needed. Read a complete schema or tightly coupled procedure when its whole contract is necessary, not every reference by default.
3. State required order only for dependencies, mutations, authorization, or cleanup. Let independent searches batch and let the agent choose routine implementation details.
4. Define completion by the requested deliverable and its applicable checks. Reuse evidence for unchanged inputs. Do not add a mandatory report, subagent round, test suite, or confirmation merely because the skill is installed.
5. Check changed triggers, links, metadata, and any affected helper behavior. For a small prose edit, summarize this review; for a new skill or broad rewrite, use references/checklist.md. Fix material failures at their source.