Writing Skills

Writing Skills

Purpose

Create the smallest reusable skill that changes decisions or improves task execution without constraining unrelated work. Skill changes use behavior validation, not a code TDD route. This validation does not require loading aegis:test-driven-development.

Default Path

1. Establish Need And Ownership

• Name the reusable behavior gap, intended users/hosts, and non-goals.
• Check whether an existing skill, project rule, host adapter, or automated check already owns it. Prefer the smallest existing owner.
• For an existing skill, inspect its references, manifests or generated copies, discovery tests, and bundled resources before changing or retiring them.
• Create a skill only for reusable, non-obvious guidance. Keep one-off project conventions in the project owner and automate mechanical constraints when practical.

2. Record Behavior Before Editing

Use representative tasks, not questions that merely ask the agent to recite instructions.

• New skill: run a no-skill control.
• For an existing skill, run the current version first; add a no-skill ablation only when testing whether the skill itself needs to exist.
• Cover positive triggers, negative near-misses, and a pressure or application case appropriate to the skill type.
• Record decisions, missed or extra invocations, unsafe workarounds, evidence references, and unknowns. Do not treat line or byte counts as behavior proof.

If meaningful behavior cannot be evaluated, stop at needs-verification; do not claim that the skill is deployment-ready or capability-preserving.

3. Design The Minimum Instruction Surface

• Assume the agent is capable. Include only non-obvious context, decision