Skills
skills/sickn33/antigravity-awesome-skills/skill-developer

skill-developer

SKILL.md

Skill Developer Guide

Purpose

Comprehensive guide for creating and managing skills in Claude Code with auto-activation system, following Anthropic's official best practices including the 500-line rule and progressive disclosure pattern.

When to Use This Skill

Automatically activates when you mention:

  • Creating or adding skills
  • Modifying skill triggers or rules
  • Understanding how skill activation works
  • Debugging skill activation issues
  • Working with skill-rules.json
  • Hook system mechanics
  • Claude Code best practices
  • Progressive disclosure
  • YAML frontmatter
  • 500-line rule

System Overview

Two-Hook Architecture

1. UserPromptSubmit Hook (Proactive Suggestions)

  • File: .claude/hooks/skill-activation-prompt.ts
  • Trigger: BEFORE Claude sees user's prompt
  • Purpose: Suggest relevant skills based on keywords + intent patterns
  • Method: Injects formatted reminder as context (stdout → Claude's input)
  • Use Cases: Topic-based skills, implicit work detection

2. Stop Hook - Error Handling Reminder (Gentle Reminders)

  • File: .claude/hooks/error-handling-reminder.ts
  • Trigger: AFTER Claude finishes responding
  • Purpose: Gentle reminder to self-assess error handling in code written
  • Method: Analyzes edited files for risky patterns, displays reminder if needed
  • Use Cases: Error handling awareness without blocking friction

Philosophy Change (2025-10-27): We moved away from blocking PreToolUse for Sentry/error handling. Instead, use gentle post-response reminders that don't block workflow but maintain code quality awareness.

Configuration File

Location: .claude/skills/skill-rules.json

Defines:

  • All skills and their trigger conditions
  • Enforcement levels (block, suggest, warn)
  • File path patterns (glob)
  • Content detection patterns (regex)
  • Skip conditions (session tracking, file markers, env vars)

Skill Types

1. Guardrail Skills

Purpose: Enforce critical best practices that prevent errors

Characteristics:

  • Type: "guardrail"
  • Enforcement: "block"
  • Priority: "critical" or "high"
  • Block file edits until skill used
  • Prevent common mistakes (column names, critical errors)
  • Session-aware (don't repeat nag in same session)

Examples:

  • database-verification - Verify table/column names before Prisma queries
  • frontend-dev-guidelines - Enforce React/TypeScript patterns

When to Use:

  • Mistakes that cause runtime errors
  • Data integrity concerns
  • Critical compatibility issues

2. Domain Skills

Purpose: Provide comprehensive guidance for specific areas

Characteristics:

  • Type: "domain"
  • Enforcement: "suggest"
  • Priority: "high" or "medium"
  • Advisory, not mandatory
  • Topic or domain-specific
  • Comprehensive documentation

Examples:

  • backend-dev-guidelines - Node.js/Express/TypeScript patterns
  • frontend-dev-guidelines - React/TypeScript best practices
  • error-tracking - Sentry integration guidance

When to Use:

  • Complex systems requiring deep knowledge
  • Best practices documentation
  • Architectural patterns
  • How-to guides

Quick Start: Creating a New Skill

Step 1: Create Skill File

Location: .claude/skills/{skill-name}/SKILL.md

Template:

---
name: my-new-skill
description: Brief description including keywords that trigger this skill. Mention topics, file types, and use cases. Be explicit about trigger terms.
---

# My New Skill

## Purpose
What this skill helps with

## When to Use
Specific scenarios and conditions

## Key Information
The actual guidance, documentation, patterns, examples

Best Practices:

  • ✅ Name: Lowercase, hyphens, gerund form (verb + -ing) preferred
  • ✅ Description: Include ALL trigger keywords/phrases (max 1024 chars)
  • ✅ Content: Under 500 lines - use reference files for details
  • ✅ Examples: Real code examples
  • ✅ Structure: Clear headings, lists, code blocks

Step 2: Add to skill-rules.json

See SKILL_RULES_REFERENCE.md for complete schema.

Basic Template:

{
  "my-new-skill": {
    "type": "domain",
    "enforcement": "suggest",
    "priority": "medium",
    "promptTriggers": {
      "keywords": ["keyword1", "keyword2"],
      "intentPatterns": ["(create|add).*?something"]
    }
  }
}

Step 3: Test Triggers

Test UserPromptSubmit:

echo '{"session_id":"test","prompt":"your test prompt"}' | \
  npx tsx .claude/hooks/skill-activation-prompt.ts

Test PreToolUse:

cat <<'EOF' | npx tsx .claude/hooks/skill-verification-guard.ts
{"session_id":"test","tool_name":"Edit","tool_input":{"file_path":"test.ts"}}
EOF

Step 4: Refine Patterns

Based on testing:

  • Add missing keywords
  • Refine intent patterns to reduce false positives
  • Adjust file path patterns
  • Test content patterns against actual files

Step 5: Follow Anthropic Best Practices

✅ Keep SKILL.md under 500 lines ✅ Use progressive disclosure with reference files ✅ Add table of contents to reference files > 100 lines ✅ Write detailed description with trigger keywords ✅ Test with 3+ real scenarios before documenting ✅ Iterate based on actual usage

Enforcement Levels

BLOCK (Critical Guardrails)

  • Physically prevents Edit/Write tool execution
  • Exit code 2 from hook, stderr → Claude
  • Claude sees message and must use skill to proceed
  • Use For: Critical mistakes, data integrity, security issues

Example: Database column name verification

SUGGEST (Recommended)

  • Reminder injected before Claude sees prompt
  • Claude is aware of relevant skills
  • Not enforced, just advisory
  • Use For: Domain guidance, best practices, how-to guides

Example: Frontend development guidelines

WARN (Optional)

  • Low priority suggestions
  • Advisory only, minimal enforcement
  • Use For: Nice-to-have suggestions, informational reminders

Rarely used - most skills are either BLOCK or SUGGEST.

Skip Conditions & User Control

1. Session Tracking

Purpose: Don't nag repeatedly in same session

How it works:

  • First edit → Hook blocks, updates session state
  • Second edit (same session) → Hook allows
  • Different session → Blocks again

State File: .claude/hooks/state/skills-used-{session_id}.json

2. File Markers

Purpose: Permanent skip for verified files

Marker: // @skip-validation

Usage:

// @skip-validation
import { PrismaService } from './prisma';
// This file has been manually verified

NOTE: Use sparingly - defeats the purpose if overused

3. Environment Variables

Purpose: Emergency disable, temporary override

Global disable:

export SKIP_SKILL_GUARDRAILS=true  # Disables ALL PreToolUse blocks

Skill-specific:

export SKIP_DB_VERIFICATION=true
export SKIP_ERROR_REMINDER=true

Testing Checklist

When creating a new skill, verify:

  • Skill file created in .claude/skills/{name}/SKILL.md
  • Proper frontmatter with name and description
  • Entry added to skill-rules.json
  • Keywords tested with real prompts
  • Intent patterns tested with variations
  • File path patterns tested with actual files
  • Content patterns tested against file contents
  • Block message is clear and actionable (if guardrail)
  • Skip conditions configured appropriately
  • Priority level matches importance
  • No false positives in testing
  • No false negatives in testing
  • Performance is acceptable (<100ms or <200ms)
  • JSON syntax validated: jq . skill-rules.json
  • SKILL.md under 500 lines ⭐
  • Reference files created if needed
  • Table of contents added to files > 100 lines

Reference Files

For detailed information on specific topics, see:

TRIGGER_TYPES.md

Complete guide to all trigger types:

  • Keyword triggers (explicit topic matching)
  • Intent patterns (implicit action detection)
  • File path triggers (glob patterns)
  • Content patterns (regex in files)
  • Best practices and examples for each
  • Common pitfalls and testing strategies

SKILL_RULES_REFERENCE.md

Complete skill-rules.json schema:

  • Full TypeScript interface definitions
  • Field-by-field explanations
  • Complete guardrail skill example
  • Complete domain skill example
  • Validation guide and common errors

HOOK_MECHANISMS.md

Deep dive into hook internals:

  • UserPromptSubmit flow (detailed)
  • PreToolUse flow (detailed)
  • Exit code behavior table (CRITICAL)
  • Session state management
  • Performance considerations

TROUBLESHOOTING.md

Comprehensive debugging guide:

  • Skill not triggering (UserPromptSubmit)
  • PreToolUse not blocking
  • False positives (too many triggers)
  • Hook not executing at all
  • Performance issues

PATTERNS_LIBRARY.md

Ready-to-use pattern collection:

  • Intent pattern library (regex)
  • File path pattern library (glob)
  • Content pattern library (regex)
  • Organized by use case
  • Copy-paste ready

ADVANCED.md

Future enhancements and ideas:

  • Dynamic rule updates
  • Skill dependencies
  • Conditional enforcement
  • Skill analytics
  • Skill versioning

Quick Reference Summary

Create New Skill (5 Steps)

  1. Create .claude/skills/{name}/SKILL.md with frontmatter
  2. Add entry to .claude/skills/skill-rules.json
  3. Test with npx tsx commands
  4. Refine patterns based on testing
  5. Keep SKILL.md under 500 lines

Trigger Types

  • Keywords: Explicit topic mentions
  • Intent: Implicit action detection
  • File Paths: Location-based activation
  • Content: Technology-specific detection

See TRIGGER_TYPES.md for complete details.

Enforcement

  • BLOCK: Exit code 2, critical only
  • SUGGEST: Inject context, most common
  • WARN: Advisory, rarely used

Skip Conditions

  • Session tracking: Automatic (prevents repeated nags)
  • File markers: // @skip-validation (permanent skip)
  • Env vars: SKIP_SKILL_GUARDRAILS (emergency disable)

Anthropic Best Practices

✅ 500-line rule: Keep SKILL.md under 500 lines ✅ Progressive disclosure: Use reference files for details ✅ Table of contents: Add to reference files > 100 lines ✅ One level deep: Don't nest references deeply ✅ Rich descriptions: Include all trigger keywords (max 1024 chars) ✅ Test first: Build 3+ evaluations before extensive documentation ✅ Gerund naming: Prefer verb + -ing (e.g., "processing-pdfs")

Troubleshoot

Test hooks manually:

# UserPromptSubmit
echo '{"prompt":"test"}' | npx tsx .claude/hooks/skill-activation-prompt.ts

# PreToolUse
cat <<'EOF' | npx tsx .claude/hooks/skill-verification-guard.ts
{"tool_name":"Edit","tool_input":{"file_path":"test.ts"}}
EOF

See TROUBLESHOOTING.md for complete debugging guide.

Related Files

Configuration:

  • .claude/skills/skill-rules.json - Master configuration
  • .claude/hooks/state/ - Session tracking
  • .claude/settings.json - Hook registration

Hooks:

  • .claude/hooks/skill-activation-prompt.ts - UserPromptSubmit
  • .claude/hooks/error-handling-reminder.ts - Stop event (gentle reminders)

All Skills:

  • .claude/skills/*/SKILL.md - Skill content files

Skill Status: COMPLETE - Restructured following Anthropic best practices ✅ Line Count: < 500 (following 500-line rule) ✅ Progressive Disclosure: Reference files for detailed information ✅

Next: Create more skills, refine patterns based on usage

Weekly Installs
10
Install
$ npx skills add sickn33/antigravity-awesome-skills --skill "skill-developer"
Repository
sickn33/antigravity-awesome-skills
Installed on
antigravity8
cursor6
claude-code5
gemini-cli5
codex4
windsurf3