Creating Skills

Creating Skills

Overview

Skills are reference guides for proven techniques, patterns, or tools. Write them to help future agents quickly find and apply effective approaches.

Skills must be discoverable (an agent can find them), scannable (quick to evaluate), and actionable (clear examples).

Core principle: Assume the agent already handles general reasoning well. Only add context the agent would not otherwise have.

When to Use

Create a skill when:

• Technique wasn't intuitively obvious
• Pattern applies broadly across projects
• You'd reference this again
• Others would benefit

Don't create for:

• One-off solutions specific to single project
• Standard practices well-documented elsewhere
• Project conventions (put those in project-level agent guidance such as AGENTS.md)

Required Structure

Frontmatter (YAML)

---
name: skill-name-with-hyphens
description: Use when [triggers/symptoms] - [what it does and how it helps]
tags: relevant-tags
---

Rules:

• Only name and description fields supported (max 1024 chars total)
• Name: letters, numbers, hyphens only (no special chars). Use gerund form (verb + -ing)
• Description: Third person, starts with "Use when..."
• Include BOTH triggering conditions AND what skill does
• Match specificity to task complexity (degrees of freedom)

Document Structure

# Skill Name

## Overview
Core principle in 1-2 sentences. What is this?

## When to Use
- Bullet list with symptoms and use cases
- When NOT to use

## Quick Reference
Table or bullets for common operations

## Implementation
Inline code for simple patterns
Link to separate file for heavy reference (100+ lines)

## Common Mistakes
What goes wrong + how to fix

## Real-World Impact (optional)
Concrete results from using this technique

Degrees of Freedom

Match specificity to task complexity:

• High freedom: Flexible tasks requiring judgment

  • Use broad guidance, principles, examples
  • Let the agent adapt approach to context
  • Example: "Use when designing APIs - provides REST principles and patterns"

• Low freedom: Fragile or critical operations

  • Be explicit about exact steps
  • Include validation checks
  • Example: "Use when deploying to production - follow exact deployment checklist with rollback procedures"

Red flag: If skill tries to constrain the agent too much on creative tasks, reduce specificity. If skill is too vague on critical operations, add explicit steps.

Skill Discovery Optimization

Critical: Agents commonly use the description to decide if a skill is relevant. Optimize for discovery.

Description Best Practices

# ❌ BAD - Too vague, doesn't mention when to use
description: For async testing

# ❌ BAD - First person in agent-facing metadata
description: I help you with flaky tests

# ✅ GOOD - Triggers + what it does
description: Use when tests have race conditions or pass/fail inconsistently - replaces arbitrary timeouts with condition polling for reliable async tests

# ✅ GOOD - Technology-specific with explicit trigger
description: Use when using React Router and handling auth redirects - provides patterns for protected routes and auth state management

Keyword Coverage

Use words an agent would match:

• Error messages: "ENOENT", "Cannot read property", "Timeout"
• Symptoms: "flaky", "hanging", "race condition", "memory leak"
• Synonyms: "cleanup/teardown/afterEach", "timeout/hang/freeze"
• Tools: Actual command names, library names, file types

Naming Conventions

Use gerund form (verb + -ing):

• ✅ creating-skills not skill-creation
• ✅ testing-with-subagents not subagent-testing
• ✅ debugging-memory-leaks not memory-leak-debugging
• ✅ processing-pdfs not pdf-processor
• ✅ analyzing-spreadsheets not spreadsheet-analysis

Why gerunds work:

• Describes the action you're taking
• Active and clear
• Consistent and action-oriented

Avoid:

• ❌ Vague names like "Helper" or "Utils"
• ❌ Passive voice constructions

Code Examples

One excellent example beats many mediocre ones.

Choose Language by Use Case

• Testing techniques → TypeScript/JavaScript
• System debugging → Shell/Python
• Data processing → Python
• API calls → TypeScript/JavaScript

Good Example Checklist

• Complete and runnable
• Well-commented explaining WHY not just what
• From real scenario (not contrived)
• Shows pattern clearly
• Ready to adapt (not generic template)
• Shows both BAD (❌) and GOOD (✅) approaches
• Includes realistic context/setup code

Example Template

// ✅ GOOD - Clear, complete, ready to adapt
interface RetryOptions {
  maxAttempts: number;
  delayMs: number;
  backoff?: 'linear' | 'exponential';
}

async function retryOperation<T>(
  operation: () => Promise<T>,
  options: RetryOptions
): Promise<T> {
  const { maxAttempts, delayMs, backoff = 'linear' } = options;

  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    try {
      return await operation();
    } catch (error) {
      if (attempt === maxAttempts) throw error;

      const delay = backoff === 'exponential'
        ? delayMs * Math.pow(2, attempt - 1)
        : delayMs * attempt;

      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }

  throw new Error('Unreachable');
}

// Usage
const data = await retryOperation(
  () => fetchUserData(userId),
  { maxAttempts: 3, delayMs: 1000, backoff: 'exponential' }
);

Don't

• ❌ Implement in 5+ languages (you're good at porting)
• ❌ Create fill-in-the-blank templates
• ❌ Write contrived examples
• ❌ Show only code without comments

File Organization

Self-Contained (Preferred)

typescript-type-safety/
  SKILL.md    # Everything inline

When: All content fits in ~500 words, no heavy reference needed

With Supporting Files

api-integration/
  SKILL.md           # Overview + patterns
  retry-helpers.ts   # Reusable code
  examples/
    auth-example.ts
    pagination-example.ts

When: Reusable tools or multiple complete examples needed

With Heavy Reference

aws-sdk/
  SKILL.md       # Overview + workflows
  s3-api.md      # 600 lines API reference
  lambda-api.md  # 500 lines API reference

When: Reference material > 100 lines

Token Efficiency

Skills load into every conversation. Keep them concise.

Target Limits

• SKILL.md: Keep under 500 lines
• Getting-started workflows: <150 words
• Frequently-loaded skills: <200 words total
• Other skills: <500 words

Challenge each piece of information: "Does the agent need this explanation?"

Compression Techniques

# ❌ BAD - Verbose (42 words)
Your human partner asks: "How did we handle authentication errors in React Router before?"
You should respond: "I'll search past conversations for React Router authentication patterns."
Then dispatch a subagent with the search query: "React Router authentication error handling 401"

# ✅ GOOD - Concise (20 words)
Partner: "How did we handle auth errors in React Router?"
You: Searching...
[Dispatch subagent → synthesis]

Techniques:

• Reference tool --help instead of documenting all flags
• Cross-reference other skills instead of repeating content
• Show minimal example of pattern
• Eliminate redundancy
• Use progressive disclosure (reference additional files as needed)
• Organize content by domain for focused context

Workflow Recommendations

For multi-step processes, include:

1. Clear sequential steps: Break complex tasks into numbered operations
2. Feedback loops: Build in verification/validation steps
3. Error handling: What to check when things go wrong
4. Checklists: For processes with many steps or easy-to-miss details

Example structure:

## Workflow

1. **Preparation**
   - Check prerequisites
   - Validate environment

2. **Execution**
   - Step 1: [action + expected result]
   - Step 2: [action + expected result]

3. **Verification**
   - [ ] Check 1 passes
   - [ ] Check 2 passes

4. **Rollback** (if needed)
   - Steps to undo changes

Common Mistakes

Flowchart Usage

Only use flowcharts for:

• Non-obvious decision points
• Process loops where you might stop too early
• "When to use A vs B" decisions

Never use for:

• Reference material → Use tables/lists
• Code examples → Use markdown blocks
• Linear instructions → Use numbered lists

Cross-Referencing Skills

# ✅ GOOD - Name only with clear requirement
**REQUIRED:** Use superpowers:test-driven-development before proceeding

**RECOMMENDED:** See typescript-type-safety for proper type guards

# ❌ BAD - Unclear if required
See skills/testing/test-driven-development

# ❌ BAD - Force-loads file, wastes context
@skills/testing/test-driven-development/SKILL.md

Advanced Practices

Iterative Development

Best approach: Develop skills iteratively with an agent

1. Start with minimal viable skill
2. Test with real use cases
3. Refine based on what works
4. Remove what doesn't add value

Build Evaluations First

Before extensive documentation:

1. Create test scenarios
2. Identify what good looks like
3. Document proven patterns
4. Skip theoretical improvements

Utility Scripts

For reliability, provide:

• Scripts with explicit error handling
• Exit codes for success/failure
• Clear error messages
• Examples of usage

Example:

#!/bin/bash
set -e  # Exit on error

if [ ! -f "config.json" ]; then
  echo "Error: config.json not found" >&2
  exit 1
fi

# Script logic here
echo "Success"
exit 0

Templates for Structured Output

When skills produce consistent formats:

## Output Template

\`\`\`typescript
interface ExpectedOutput {
  status: 'success' | 'error';
  data: YourDataType;
  errors?: string[];
}
\`\`\`

**Usage**: Copy and adapt for your context

Skill Creation Checklist

Before writing:

• Technique isn't obvious or well-documented elsewhere
• Pattern applies broadly (not project-specific)
• I would reference this across multiple projects

Frontmatter:

• Name uses only letters, numbers, hyphens
• Description starts with "Use when..."
• Description includes triggers AND what skill does
• Description is third person
• Total frontmatter < 1024 characters

Content:

• Overview states core principle (1-2 sentences)
• "When to Use" section with symptoms
• Quick reference table for common operations
• One excellent code example (if technique skill)
• Common mistakes section
• Keywords throughout for searchability

Quality:

• Word count appropriate for frequency (see targets above)
• SKILL.md under 500 lines
• No narrative storytelling
• Flowcharts only for non-obvious decisions
• Supporting files only if needed (100+ lines reference)
• Cross-references use skill name, not file paths
• No time-sensitive information
• Consistent terminology throughout
• Concrete examples (not templates)
• Degrees of freedom match task complexity

Testing (if discipline-enforcing skill):

• Tested with subagent scenarios
• Addresses common rationalizations
• Includes red flags list

Directory Structure

skills/
  skill-name/
    SKILL.md              # Required
    supporting-file.*     # Optional
    examples/             # Optional
      example1.ts
    scripts/              # Optional
      helper.py

Flat namespace - all skills in one searchable directory

Real-World Impact

Good skills:

• Future agents find them quickly through discovery optimization
• Can be scanned in seconds (quick reference)
• Provide clear actionable examples
• Prevent repeating same research
• Stay under 500 lines (token efficient)
• Match specificity to task needs (right degrees of freedom)

Bad skills:

• Get ignored (vague description)
• Take too long to evaluate (no quick reference)
• Leave gaps in understanding (no examples)
• Waste token budget (verbose explanations of obvious things)
• Over-constrain creative tasks or under-specify critical operations
• Include time-sensitive or obsolete information

Remember: Skills are for future agents, not current you. Optimize for discovery, scanning, and action.

Golden rule: Assume the agent already handles general reasoning well. Only add context the agent would not otherwise have.