Copilot Skill Builder

Skill Builder

This skill helps you create, organize, and maintain Agent Skills for GitHub Copilot and compatible AI agents.

What are Agent Skills?

Agent Skills are folders containing a SKILL.md file plus optional scripts, examples, and resources. They teach specialized capabilities and workflows to AI agents. Skills are:

• Portable: Work across VS Code, Copilot CLI, and Copilot coding agent
• Composable: Multiple skills can work together
• Efficient: Loaded on-demand based on relevance to the current task
• Open standard: Based on agentskills.io

Skill locations

SKILL.md file format

Every skill requires a SKILL.md file with YAML frontmatter:

---
name: skill-name
description: Description of what the skill does and when to use it (max 1024 chars)
---

# Skill Instructions

Detailed instructions, guidelines, and examples...

Frontmatter fields

Body content

The skill body should include:

1. Purpose: What the skill accomplishes
2. When to use: Specific triggers and use cases
3. Step-by-step procedures: Clear instructions to follow
4. Examples: Expected inputs and outputs
5. Resource references: Links to included scripts/files using relative paths

Creating a new skill

Step 1: Create the skill directory

mkdir -p .github/skills/<skill-name>

Step 2: Create SKILL.md

Create .github/skills/<skill-name>/SKILL.md with:

• YAML frontmatter with name and description
• Clear instructions in the Markdown body
• References to any additional resources

Step 3: Add optional resources

Add any supporting files to the skill directory:

• Scripts (e.g., test-template.js, deploy.sh)
• Examples (e.g., examples/basic.json)
• Documentation (e.g., README.md, troubleshooting.md)

Reference these files using relative paths in your SKILL.md:

Use the [test template](./test-template.js) as a starting point.
See [examples](./examples/) for common scenarios.

Best practices

Writing effective descriptions

The description determines when Copilot loads your skill. Be specific:

✅ Good: "Debug GitHub Actions workflows by analyzing logs, identifying common failures, and suggesting fixes"

❌ Bad: "Help with GitHub Actions"

Keeping skills focused

• One skill = one capability or workflow
• Avoid kitchen-sink skills that try to do everything
• Compose multiple focused skills for complex workflows

Managing skill size

• Skills load progressively (metadata → instructions → resources)
• Keep SKILL.md focused on instructions
• Put detailed documentation in separate files

Security considerations

• Review shared skills before using them
• Be cautious with skills that run shell commands
• Use VS Code's terminal tool controls for script execution

Example skill structure

.github/skills/
└── webapp-testing/
    ├── SKILL.md              # Main skill file
    ├── test-template.js      # Reusable test template
    ├── playwright.config.ts  # Example config
    └── examples/
        ├── login-test.js
        └── api-test.js

Reference documentation

• Agent Skills in VS Code
• Agent Skills standard
• Reference skills repository
• Awesome Copilot community collection

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