Writing Kit Skills

writing-kit-skills

A kit skill exists to make an agent take the same process every run. Every rule here serves that predictability at the lowest token cost that still binds weaker CLIs — this kit installs standalone into many runtimes, so redundancy is spent deliberately, never by accident.

The skeleton

Every SKILL.md follows this order, skipping sections it genuinely doesn't need:

1. Definitional opener — one or two sentences stating what the skill produces and the boundary that makes it this skill and not a neighbour. No ## Purpose heading, no restatement of the frontmatter description.
2. Inputs — what must be known before work starts, and the stop-and-ask rule for anything missing.
3. Rules — the binding constraints. Each prohibition is paired with the positive action ("Dispatch fires only on explicit user say-so; until then, keep capturing"), and may carry one clause of rationale. No second section restating rules in negated form.
4. Process / Workflow / Modes — ### N. Verb-phrase steps or named modes. Each step ends where an agent can tell done from not-done.
5. The artifact (when the skill writes one) — template plus two or three filled sample rows at most; full examples live in references/.
6. Output — the exact chat surface: templates, caps, and the stop.
7. Completion criteria — observable checks only (a path that exists, a command output, a read-back match, a git status state). Never checklist items that re-assert body rules; the body already binds them.

Word budget

A SKILL.md runs 1,000–1,300 words; 1,500 (body only, after the closing ---) is the validator-enforced ceiling. Over budget → move mechanics and long examples to references/; never hit budget by thinning refusal or safety language.

Voice and language

• Imperative, present tense. Sentence-case headings ("Trigger discipline", not "Trigger Discipline").
• Say each fact once per file. The description states identity; the body never re-narrates it.
• Prefer a leading word over a restated triad ("Decisions are artifacts", "stop signal", "evidence") — one pretrained concept the agent thinks with.
• One example per pattern. Good/bad pairs only where the distinction is the lesson.
• No invented abbreviations or arrow-chain prose in agent-facing output rules; arrows as notation inside instruction text are fine.
• One-clause rationale after a rule is house style ("dead routing rules cost every session tokens"); paragraph-length justification is not.

Canonical one-liners

These five lines are shared kit protocol. Paste them byte-exact (validator-enforced); never paraphrase or expand them:

• Resolve `: the *.code-workspace directory if one exists, else the per-context root (CONTEXT-MAP.md` at repo root), else the repo root.
• If graphify-out/graph.json exists (project root, else workspace root), query it before raw search; older than ~7 days → suggest graphify update .; missing → skip graphify.
• Sub-agents: dispatch local lanes automatically for independent work — never cloud agents; announce the lane count at dispatch and report each lane as it completes.
• Name the full PROJECT-CODE from the Project Matrix everywhere; never mix one project's conventions, tokens, or components into another.
• Emit Stage / Found / Next / Needs user at each phase transition — one line per field.

Output caps

Every surface where the agent emits text carries an explicit bound:

• Reports: ≤3 bullets per section unless the section justifies more in its own text.
• Evidence: quote the shortest decisive tail (the pass/fail line and counts); link or name the rest.
• Suggested next skills (optional) footer: 1–3 items, advisory, never gating.
• Phase updates: one line per field.
• Interviews: one question at a time, leading with the recommended answer so the user can accept it in a word.

The auto-clarity valve

Compression never touches: refusal boundaries and scope gates (AGENTS.md rule 7 — they are the safety property), irreversible-action confirmations, and multi-step sequences where terseness would blur order or dependencies. Write those in full prose.

Frontmatter and gates

• description: is the router. Model-invoked skills get identity + one trigger per genuinely distinct branch — synonym stacks are duplication; collapse them. Keep negative-routing clauses ("X routes to /other instead") and legacy aliases (the "(PRD)" spec alias) — they are branches, not synonyms.
• Any description: edit or new skill invalidates the eval-provenance snapshot (validate.sh check 10) and requires a user-run trigger-eval sweep plus score.py --write-snapshot before it can land. Batch description work; never restamp last_run by hand.
• disable-model-invocation: true ⇔ agents/openai.yaml with allow_implicit_invocation: false (cross-runtime parity, validator-enforced).
• Keep any description containing : double-quoted (strict-YAML parse, check 1).

Failure modes to hunt

Sediment — layers that settle because adding feels safe; prune on every edit. Sprawl — over budget even when every line is live; cure by disclosure to references/, not by thinning safety language. Duplication — the same meaning twice in one file (description↔body, rules↔checklist); keep one. No-op — a line the agent already obeys by default; delete the sentence, don't trim it. Phantom tooling — documented commands or pointers that don't hold: a flag absent from the script's --help, a reference committed as placeholder scaffolding. If scripts ever land, flag↔--help parity becomes a validator check.

Completion criteria

• [ ] bash tools/validate.sh passes (or fails only on check 10 when the edit is a batched description/new-skill change awaiting the user's eval sweep)
• [ ] Word count within budget: awk 'NR==1&&/^---$/{f=1;next} f==1&&/^---$/{f=2;next} f==2&&NF{c+=NF} END{print c+0}' skills//SKILL.md ≤ 1,500
• [ ] Every refusal/stop line present in the previous version is present (or strengthened) in the new one — verified by diff, not recollection
• [ ] Frontmatter untouched unless this is an approved description batch
• [ ] Sync map satisfied: manifest row, README row, duplicated-by-design copies edited together

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: devarfeen
• Source: devarfeen/agent-skills-kit
• License: MIT

Install and usage instructions live in the source repository linked above.