Skill Creator

skill-creator

Build, validate, and iterate agent skills in this monorepo. Bakes in the conventions every skill here follows: kebab-case naming, "Use when" trigger phrases in the description, and selective XML for example boundaries.

Workflow

1. Discover

Clarify what the skill should do. Answer these before scaffolding:

1. What user request triggers this skill? Capture verbatim phrases.
2. Does an existing skill in skills/ already cover this? Run ls skills/ and skim each SKILL.md description.

If overlap is >70%, propose extending the existing skill instead.

2. Name

Apply references/naming.md. Quick check:

• kebab-case-with-hyphens only
• Matches ^[a-z][a-z0-9-]+[a-z0-9]$
• ≤64 chars
• No abbreviations like bestpractices — use best-practices
• Prefer <domain>-<focus> (e.g., ts-best-practices) over generic <thing>-rules

3. Draft frontmatter

Skills here are agent-agnostic: name and description are universally required (the skills CLI rejects skills missing either); the others are Claude Code extensions kept for cross-agent compatibility (other agents ignore them). Full schema in references/frontmatter.md.

---
name: <skill-name>
description: >-
  This skill should be used when [trigger condition]. Common triggers
  include "verbatim phrase 1", "verbatim phrase 2", and "verbatim phrase 3".
  [What it bakes in / what's distinctive]. Skip when [anti-trigger].

# --- Claude Code extensions (ignored by other agents) ---
argument-hint: '[<optional-arg>]'
user-invocable: true
# Optional, defaults to false:
# disable-model-invocation: true  # set true to prevent the model from auto-loading this skill
---

name must exactly match the skill's directory name (kebab-case).

Description rules (full list):

• 80–1024 characters
• Contains "Use when" or "This skill should be used when"
• Lists ≥3 verbatim trigger phrases in double quotes
• No anti-shortcut words: then, next, step 1, process, first — these get followed as instructions instead of treated as triggers
• Includes a Skip when clause naming what the skill does NOT do

4. Draft body

Markdown headings (## ..., ### ...) for structure. XML only inside these tags (when to use which):

• <example> for full scenarios
• <good> / <bad> for contrast pairs
• <input> / <output> for tool-call boundaries

Typical body sections (per the agents-skills baseline spec: "Step-by-step instructions, Examples of inputs and outputs, Common edge cases"):

• ## Workflow — numbered actions the agent takes
• ## Examples — at least one <example> block
• ## References — links to companion docs

Do not add ## When to use / ## When NOT to use body sections. Routing signal (when to invoke, when to skip) lives only in the frontmatter description — that's all dispatchers see before activation. The body loads after activation and is for executing the skill: workflow steps, examples, edge cases. Duplicating triggers in the body wastes tokens and creates drift risk.

5. Self-lint

Run pnpm skill-toolkit lint <name>. All error-severity findings must clear; warn and info are advisory. If any rule fails, fix the SKILL.md and re-run.

The full rule list lives in references/lint-checklist.md. The TS implementation in packages/skill-toolkit/src/lint/rules.ts is the enforcer.

6. Capture rationalizations (discipline skills only)

If this is a discipline skill (one that enforces rules the agent might rationalize skipping — e.g., "always run tests", "never use any", "always use Result"), dispatch a subagent against a realistic prompt where the rule is tempting to skip. Read the response. When the agent explained why it skipped a rule, capture the excuse verbatim into a ## Rationalization table section at the bottom of SKILL.md.

Format:

## Rationalization table

| Skipped rule                | Verbatim excuse                   | Why it's wrong                                  |
| --------------------------- | --------------------------------- | ----------------------------------------------- |
| Always run the test         | "the change is tiny so I'll skip" | Tiny changes still break behavior; run the test |
| Use Result instead of throw | "this is just a quick prototype"  | Prototypes leak into prod; use Result anyway    |

Capturing excuses verbatim — not sanitized — is the point. Future agents recognize their own pattern. Skip this step only when the skill has no rules an agent could rationalize skipping (most reference skills, some pattern skills). Technique and discipline skills almost always benefit from a rationalization table.

7. Package

Write to skills/<name>/:

• SKILL.md — the skill body
• LICENSE — MIT (matches repo root)
• README.md — human-facing summary

Optional companions for non-trivial skills:

• references/<topic>.md — deeper rules referenced from SKILL.md
• templates/<thing>.template — boilerplate the skill scaffolds from

Examples

The <bad> example fails three rules: no "Use when" phrase, no verbatim trigger phrases in quotes, contains anti-shortcut words ("first", "then", "process") that cause the agent to follow them as instructions instead of treating them as triggers.

References

• references/frontmatter.md — frontmatter schema
• references/naming.md — naming rules
• references/description.md — description rules + anti-shortcut patterns
• references/xml-usage.md — when to use XML vs Markdown
• references/lint-checklist.md — full self-lint checklist

Templates

• templates/SKILL.md.template — boilerplate with placeholders
• templates/README.md.template — readme boilerplate
• templates/example-skill.md — fully-worked example skill