Create Ultimate Skill

Creation Workflow

When creating a new skill based on user's request: $ARGUMENTS

Phase 1: Define Use Cases

Ask the user:

• Use cases: "Describe 2-3 specific scenarios where you'd want this skill to activate. What would you say to Claude, and what should it do?"

• Non-use cases: "What should this skill NOT be used for?" (defines negative triggers)

Phase 2: Choose Archetype and Scope

Ask the user:

• Archetype (see Archetypes section below)

• Triggers: What phrases should activate this skill?

• Scope: What's in scope vs out of scope?

Phase 3: Fetch Latest Documentation

Fetch the latest official skill documentation to verify current fields and constraints:

WebFetch: https://markdown.new/https://code.claude.com/docs/en/skills.md

Phase 4: Choose Save Location

Use AskUserQuestion:

• Personal (home folder): ~/.claude/skills/<skill-name>/

• available in all projects

• Project folder: .claude/skills/<skill-name>/

• project-specific

• Existing plugin: ask which plugin, then plugins/<plugin-name>/skills/

Phase 5: Create the Skill

Scaffold with init_skill.py or create manually:

python .claude/skills/create-ultimate-skill/scripts/init_skill.py <skill-name> --path <location>

Then write SKILL.md applying all rules below. Review with the checklist before presenting to user.

Phase 6: Summary

When complete, provide:

• Skill location and how to trigger it

• What it does

• Suggestions for improvement

• Testing prompts the user can try

Frontmatter Hard Rules

• description MUST be a single-line plain string. NEVER use YAML multi-line indicators (>- , | , > , |- ). Multi-line descriptions break frontmatter parsing.

• allowed-tools MUST be a single-line comma-separated string (e.g. allowed-tools: Read, Write, Edit ). NEVER use YAML list syntax.

Required Fields

Field Constraints

name

Max 64 chars, [a-z0-9-] only, no "anthropic"/"claude"

description

Max 1024 chars, non-empty, no XML tags

Optional Fields

Field Purpose Example

allowed-tools

Limit tool access Read, Grep, Glob

model

Override model sonnet , opus

context

Isolation fork

agent

Subagent type Explore , Plan

hooks

Lifecycle events PreToolUse , PostToolUse , Stop

user-invocable

Slash menu visibility false to hide

disable-model-invocation

Block Skill tool true

See references/api-reference.md for full field documentation.

Archetypes

Archetype Best For Structure

CLI Reference Tool documentation Commands grouped by function, minimal prose

Methodology Workflows, processes Philosophy + THE EXACT PROMPT + examples

Safety Tool Validation, security Threat model + risk tiers + rules

Orchestration Multi-agent coordination Quick start + APIs + integrations

See references/archetypes.md for templates.

Description Rules

• Third person always ("Processes files" not "I help you")

• Include WHAT it does AND WHEN to trigger

• Specific trigger phrases users would say

• Add negative triggers ("Do NOT use for...") to prevent over-triggering

• Max 1024 characters

Template:

description: [What it does]. Use when [triggers]. Do NOT use for [exclusions].

Examples:

description: Extract text and tables from PDF files, fill forms, merge documents. Use when working with PDF files or when user mentions PDFs, forms, or document extraction.

description: Process and transform CSV data files. Use when working with CSV imports, exports, or data cleaning. Do NOT use for Excel files (.xlsx) or database queries.

SKILL.md Body Rules

• Imperative voice ("Extract the data", "Run validation")

• Never second person ("You should...")

• Concise - challenge each line: "Does Claude need this?"

• Under 500 lines, under 5,000 words (~2,000 ideal)

• Put critical instructions at the top of the file

• Use scripts for validation where possible - code is deterministic, language interpretation is not

• "Take your time to do this thoroughly" is more effective in user prompts than in SKILL.md

Structure Rules

skill-name/ ├── SKILL.md # Core guidance only ├── references/ # Detailed docs (on-demand) ├── examples/ # Working code samples └── scripts/ # Executable utilities

• References ONE level deep only - no chains

• Long files (>100 lines): include TOC

• Never include README.md in skill folder (SKILL.md IS the readme)

• Forward slashes only (no Windows paths)

Anti-Patterns

Anti-Pattern Fix

Vague descriptions Specific triggers + negative triggers

Deeply nested references One level deep

README.md in skill folder Delete it - SKILL.md IS the readme

or in description

YAML list for allowed-tools Comma-separated string

Testing

Define success criteria before building:

• Quantitative: Trigger rate >90% of relevant queries, correct tool sequence, task completes without user intervention

• Qualitative: Output matches expected format, no hallucinated commands, consistent across sessions

Debug technique: Ask Claude "When would you use the [skill name] skill?" - the response reveals how Claude interprets the description.

Test three areas:

• Triggering: Direct trigger phrases, paraphrased requests, and edge cases that should NOT trigger

• Functional: Run each use case end-to-end, check output format and accuracy

• Performance: Compare skill-assisted vs manual - does the skill save time and improve quality?

Pro tip: Iterate on a single challenging task until Claude succeeds, then extract the winning approach into the skill. This grounds design in proven patterns rather than theory.

Iteration Signals

Signal Fix

Skill never activates Add more trigger phrases to description

Wrong skill activates Add "Do NOT use for..." negative triggers

Output is wrong Refine SKILL.md instructions, add examples

Output is inconsistent Reduce degrees of freedom, be more prescriptive

Utility Scripts

init_skill.py

python .claude/skills/create-ultimate-skill/scripts/init_skill.py <skill-name> --path <location>

Creates SKILL.md with template, plus scripts/, references/, assets/ directories.

package_skill.py

python .claude/skills/create-ultimate-skill/scripts/package_skill.py <path/to/skill> [output-dir]

Validates and creates distributable zip. Checks frontmatter, naming, ensures no TODOs remain.

Skill Review Mode

When reviewing an existing skill (triggered by --review or "review my skill"):

• Read SKILL.md frontmatter, body, and supporting directories

• Categorise issues by severity:

• Critical: Won't trigger or wrong output (missing description, vague triggers, broken refs)

• Major: Significantly reduces effectiveness (>5,000 words, no progressive disclosure)

• Minor: Polish (inconsistent terminology, missing TOC, no negative triggers)

• Generate structured review report:

Skill Review: [skill-name]

Summary

[Assessment, word counts, structure]

Description Analysis

Current: [description] Issues: [with severity] Suggested: "[improved version]"

Issues by Severity

Critical ([count])

• [File]: [Issue] - [Fix]

Major ([count])

• [File]: [Issue] - [Fix]

Minor ([count])

• [File]: [Issue] - [Suggestion]

Rating: [Pass / Needs Improvement / Needs Major Revision]

Priority Fixes

1. [Highest impact]
2. [Second]
3. [Third]

Review Checklist

• Use cases: 2-3 concrete scenarios defined

• name: lowercase, hyphens, ≤64 chars

• description: single-line plain string, third person, specific triggers, ≤1024 chars

• description: negative triggers if needed

• SKILL.md body: <500 lines, <5,000 words

• No README.md in skill folder

• References: one level deep

• Forward slashes only

• Examples concrete, not abstract

Latest Documentation

Before finalising any skill's frontmatter, fetch the latest official documentation to check for new fields, changed constraints, or updated rules:

WebFetch: https://markdown.new/https://code.claude.com/docs/en/skills.md

Further Reading

• Skill Archetypes

• Official API Reference