Create Skill

Create Skill

Author new agent skills — and audit existing ones — against the best practices distilled from Anthropic's official Skill authoring guide and the patterns already in this repo. Output is a complete skill directory plus the agent-skills.git symlink wiring and inventory updates.

> This SKILL.md is a thin index. Detailed authoring rules live in > rules/*.md and load on demand. Worked examples live in > references/*.md. Literal scaffolding templates live in > templates/*.md. Reading them all up-front would burn tokens you do not > need yet — load only what the current phase asks for.

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Mode Detection

Parse $ARGUMENTS (first token) and detect the mode:

| Mode | Default | Trigger | | ---------- | ------- | ------------------------------------------------------------------------ | | scaffold | yes | Default. "create", "scaffold", "new skill", or no mode argument. | | review | | "review", "audit", "check this skill", or $0 == "review". | | upgrade | | "upgrade", "split", "convert to multi-file", or $0 == "upgrade". | | diagnose | | "diagnose", "why did miss this", or $0 == "diagnose". |

If the user typed a path or skill name as $ARGUMENTS, treat it as the target for review/upgrade/diagnose; for scaffold it is the proposed skill name.

State the detected mode and target in one line before continuing. Example:

Mode: scaffold
Target: skills///

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Scaffold Workflow (default)

A six-phase pipeline. Each phase has a gate; do not proceed until it passes.

| Phase | Name | Gate | | ----- | --------------------- | ------------------------------------------------------------- | | 0 | Requirements | User confirmed name, description, modes, structure choice | | 1 | Structure decision | Single-file vs multi-file decided with reasoning | | 2 | Frontmatter draft | Name + description + flags pass validation | | 3 | File generation | All planned files written, none over budget | | 4 | Wiring & inventories | Symlinks created (if local-dev), CLAUDE.md + README.md updated | | 5 | Self-check | Every checklist item in rules/quality-checklist.md passes |

Phase 0 — Requirements (interview)

Ask the user — in one message, batched, so they answer once:

1. Working name (kebab-case, ≤ 64 chars). What should the directory and

name: field be?

1. One-line purpose — what does this skill do? Phrased as a third-person

action ("Reviews X for Y", not "Helps you with X").

1. Trigger phrases — what would the user (or another agent) type to

reach for this skill? Collect 3–8 phrases.

1. Invocation control — slash-only (disable-model-invocation: true),

model-invokable (default), or hidden background (user-invocable: false)? See rules/invocation-control.md.

1. Modes — does the skill have one mode or several? If several, list

them with a one-line description each.

1. Inputs — does the skill take $ARGUMENTS? Positional ($0, $1)?

None?

1. Tools — should allowed-tools pre-approve any specific tools (e.g.

Bash(git *))? Default: leave unset.

1. Scope — is this an advisory skill (read-only), an applied skill

(writes code), an orchestrator (calls other skills), a slash command, or a workflow companion?

Confirm the answers back to the user verbatim before moving on. Do not guess any of these.

Phase 1 — Structure decision

Decide: single-file or multi-file? Apply this decision flow before generating anything — see rules/structure-decision.md for the full rubric.

Quick decision table:

| Signal | Pick | | --------------------------------------------------- | -------------- | | Body fits comfortably under 200 lines | Single-file | | Body would exceed 500 lines (the hard cap) | Multi-file | | 3+ orthogonal concerns (e.g. naming + architecture + tests) | Multi-file (one rule per concern) | | Worked examples > 100 lines | Move to references/ | | Reusable boilerplate the skill emits literally | Move to templates/ | | One mode and one concern | Single-file |

Output the chosen layout as a tree before writing files. In this repo the directory is nested one level under a category (workflow/, quality/, delivery/, testing/, design/, analysis/, or authoring/ — see rules/repository-conventions.md):

skills///
├── SKILL.md
├── rules/...
├── references/...
└── templates/...

Phase 2 — Frontmatter draft

Draft the YAML frontmatter using rules/frontmatter.md and rules/description-writing.md. Validate before writing:

• name is kebab-case, ≤ 64 chars, no reserved words (anthropic, claude).
• description is third-person, ≤ 1024 chars, includes both what and

when (trigger phrases), front-loaded with the most important keywords.

• disable-model-invocation: true is set if the user picked slash-only.
• argument-hint is set (unless the skill is user-invocable: false),

derived from the Modes (Q5) and Inputs (Q6) answers from Phase 0. Mirror the actual modes / flags; use […] for optional, ` for placeholders, | for alternatives. If the skill takes no arguments, emit argument-hint: ''` explicitly rather than omitting the field.

• metadata.tags are populated (5–10 specific terms).

Phase 3 — File generation

Write each planned file. For each one:

• SKILL.md — start from templates/SKILL.minimal.md (single-file) or

templates/SKILL.multi-file.md (index pattern). Keep body ≤ 500 lines.

• rules/.md — start from templates/rule.md. One file per

concern. Keep each rule self-contained; each must be loadable in isolation.

• references/.md — start from templates/reference.md. Add a

table of contents at the top if the file exceeds 100 lines (Claude partial-reads long files; the TOC is the safety net).

• templates/.md — literal text the skill emits. No prose

meta-commentary inside templates.

After each file, verify:

• Code fences declare a language identifier.
• Sentences end with full stops.
• One sentence per line (semantic line breaks) — repo prose rule.
• No backslash-style paths. No time-sensitive claims ("after August 2025").

Phase 4 — Wiring & inventories

If the user runs the local-dev symlink chain (the default for this repo), follow rules/repository-conventions.md to:

1. Place the skill at skills/// (categories: workflow,

quality, delivery, testing, design, analysis, authoring).

1. Run bash scripts/sync-symlinks.sh from the repo root to wire the

two-tier chain (~/.claude/skills/ → ~/.agents/skills/ → /skills//) — never ln -s by hand, and never invoke the script with sh.

1. Verify both hops with readlink.
2. Append an entry to the inventory in CLAUDE.md (under the matching

### \/\`` subsection, with the correct type marker).

1. Append a row to the table in README.md and add the skill to the

"Repository Structure" tree at the bottom of the README.

If the user is publishing the skill via npx skills add only, skip steps 2–3 but still update the inventories.

Phase 5 — Self-check

Run the full checklist in rules/quality-checklist.md. Treat any unchecked item as a defect — fix it before declaring the skill done.

Report the result inline as:

Self-check: PASS (28/28)

or, on failure:

Self-check: FAIL — fix these:
- [ ] description over 1024 chars (currently 1180)
- [ ] rules/architecture.md over 500 lines without TOC

---

Review Workflow

For review mode, do not write any files. Read the target skill (the path or skill name from $ARGUMENTS) and produce a structured report:

1. Load rules/quality-checklist.md.
2. Read the target SKILL.md. If it has rules/, references/,

templates/, list each file with line count.

1. For every checklist item, mark PASS / WARN / FAIL with one line of

evidence (file path + line number where applicable).

1. End with a prioritised "Top 3 fixes" list — biggest token / clarity wins

first.

Do not mutate the skill in review mode.

Upgrade Workflow

For upgrade mode, take a single-file skill and split it into multi-file:

1. Read the target SKILL.md.
2. Identify orthogonal concerns (each H2 section is a candidate).
3. Propose a layout tree (rules/, references/, templates/) and **show

it to the user for approval before writing**.

1. Move each concern into its own rule file. Replace the section in

SKILL.md with a one-line pointer + link to the new file.

1. Re-run the Phase 5 self-check.

---

Diagnose Workflow

For diagnose mode, do not scaffold or review. Analyse a session in which another skill executed and produced an unsatisfactory result, identify which of that skill's gates should have caught it, and emit a confidence-gated unified diff that hardens the target skill against the same failure class.

The full procedure (seven steps, including the mandatory confidence(analysis) ≥ 90 % gate before --apply), the report format, and the hard rules live in [rules/diagnose-mode.md](./rules/diagnose-mode.md).

Invocation:

/create-skill diagnose  [--symptom "..."] [--scope ] [--apply] [--pr] [--no-write]

The target declares its own diagnostic surface in skills//rules/diagnostic-surface.md (skills) or agents//rules/diagnostic-surface.md (agents) — phase model, failure taxonomy, existing-guards table, source root, hard invariants. Step 1 of Diagnose Mode disambiguates by checking both locations. The contract spec is in [rules/diagnostic-surface.md](./rules/diagnostic-surface.md); the scaffolding template a target drops into its own rules/ is [templates/diagnostic-surface.template.md](./templates/diagnostic-surface.template.md).

If the target has not declared a surface, Diagnose Mode falls back to inferring phases from the target body's H2 sections (SKILL.md for skills, agents/.md for agents) and warns the user once that fidelity is reduced.

Diagnose Mode never modifies user product code. It only proposes changes to the target's own source.

Self-improving skills. An orchestrator skill can close the loop further with a two-tier self-improvement loop: a fast episodic-lessons tier (persistent-memory) feeding the slow diagnose tier via a recurrence gate. The reusable recipe — including when NOT to add one — is in [rules/self-improvement-loop-pattern.md](./rules/self-improvement-loop-pattern.md). When a target declares a ## Lessons scope, Diagnose Mode reads it as evidence (Step 2).

---

Required Reading by Phase

Load these on demand — do not preload them all.

| Phase | Files | | -------- | --------------------------------------------------------------------------------------- | | 0 | rules/description-writing.md, rules/invocation-control.md | | 1 | rules/structure-decision.md, rules/progressive-disclosure.md | | 2 | rules/frontmatter.md, rules/description-writing.md | | 3 | rules/token-economics.md, rules/anti-patterns.md, plus templates in templates/ | | 4 | rules/repository-conventions.md | | 5 | rules/quality-checklist.md | | diagnose | rules/diagnose-mode.md, rules/diagnostic-surface.md, plus the target's rules/diagnostic-surface.md | | loop | rules/self-improvement-loop-pattern.md (adding a self-improvement loop to an orchestrator skill) |

Worked examples in references/skill-archetypes.md are optional — load only when the user asks "what does an X-shaped skill look like?".

---

Core Principles

1. Concise is key. The context window is a public good. Every line in

SKILL.md is a recurring token cost once loaded — write nothing Claude already knows. See rules/token-economics.md.

1. Progressive disclosure beats one big file. Three tiers: metadata

(always loaded), SKILL.md (loaded on trigger), supporting files (loaded on demand). Keep references one level deep.

1. Description is the discovery surface. Third person, what + when,

front-loaded with trigger keywords. The first 1024 chars decide whether Claude even loads the rest.

1. Match degrees of freedom to the task. Prescriptive scripts for

fragile sequences; high-freedom prose for judgment calls. See rules/structure-decision.md.

1. One skill, one job. Resist the mega-skill. Split into companions and

compose with Skill() calls.

1. Test the skill end-to-end before declaring done. Run the Phase 5

checklist; if you can, dispatch a fresh agent to use the skill on a sample task and observe.

---

Anti-patterns (one-liner — full list in rules/anti-patterns.md)

• Vague descriptions ("Helps with documents").
• First-person voice in description ("I can help you …").
• Time-sensitive claims ("after August 2025 …").
• Deeply nested references (SKILL.md → a.md → b.md → c.md).
• Mega-skills doing five jobs.
• Backslash paths.
• Reserved words (anthropic, claude) in the name.

---

Definition of Done

A scaffold run is done when:

• [ ] All planned files written and within their line caps.
• [ ] name and description validate against the rules in

rules/frontmatter.md.

• [ ] Symlinks resolve (local-dev) or npx skills install path documented.
• [ ] Inventory rows in CLAUDE.md and README.md added.
• [ ] Phase 5 self-check is PASS.
• [ ] One sentence summary delivered to the user with the install command

they can run to start using the skill.

A diagnose run is done when:

• [ ] Target skill name resolved and source root verified writable.
• [ ] Diagnostic surface loaded (or fallback warning printed).
• [ ] Failure classified against the target's taxonomy (or F-novel plus a

proposed new row).

• [ ] Phase-attribution table walks every phase in the target's surface.
• [ ] Exactly one improvement proposal constructed (one diff per report).
• [ ] confidence(analysis) score recorded; --apply honored only at

≥ 90 % (final score, after Step 6.5's two-iteration refinement loop if the initial score was below the gate).

• [ ] Report written to .agent/{branch}/diagnose-{target}.md (or

stdout with --no-write).

• [ ] If --apply ran, user explicitly confirmed before git apply.

Source & license

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

• Author: mthines
• Source: mthines/agent-skills
• License: MIT

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