Skill Creator

Create AI agent skills that work across Claude Code, Codex, and Cursor.

Workflow

1. Claude is canonical - Always create/edit in .claude/skills/<name>/ first
2. Replicate with CLI - Copy to .codex/skills/ and .cursor/skills/ using cp -r
3. Format differences - Use sed only if agent-specific tweaks are needed (rare)

Directory Structure

.claude/skills/<skill-name>/
├── SKILL.md          # Required - instructions + metadata
├── references/       # Optional - supporting documentation
├── scripts/          # Optional - executable helpers
└── assets/           # Optional - templates, resources

.codex/skills/<skill-name>/   # Copy of Claude's
.cursor/skills/<skill-name>/  # Copy of Claude's

SKILL.md Format

---
name: skill-name # Required: lowercase, hyphens, max 64 chars
description: What it does... # Required: triggers auto-selection by agent
allowed-tools: Read, Grep, Bash # Optional: Claude-specific (ignored by others)
model: claude-opus-4-5-20251101 # Optional: Claude-specific (ignored by others)
---
# Skill Title

Instructions in markdown...

Required Fields

• name: Lowercase with hyphens, must match directory name
• description: Explains what the skill does and when to use it. Include keywords users would say to help the agent auto-select this skill.

Optional Fields (Claude-specific, ignored by other agents)

• allowed-tools: Tools the agent can use without asking permission
• model: Override the model for this skill
• context: fork: Run in isolated subagent context

Creating a New Skill

1. Ask the user what the skill should do
2. Choose a descriptive name (lowercase, hyphens)
3. Create the Claude skill:

   mkdir -p .claude/skills/<name>

4. Write .claude/skills/<name>/SKILL.md with proper frontmatter
5. Replicate to other agents:

   cp -r .claude/skills/<name> .codex/skills/
   cp -r .claude/skills/<name> .cursor/skills/

Modifying an Existing Skill

1. Edit .claude/skills/<name>/SKILL.md (canonical source)
2. Replicate changes:

   cp .claude/skills/<name>/SKILL.md .codex/skills/<name>/
   cp .claude/skills/<name>/SKILL.md .cursor/skills/<name>/

Best Practices

• Keep skills focused on a single capability
• Write clear descriptions with keywords for auto-discovery
• Use references/ for lengthy documentation to keep SKILL.md concise
• Test the skill by asking the agent to perform the task