# Copilot Skill Builder

> A meta-skill that teaches how to create and maintain Agent Skills for Copilot CLI. Use this skill when the user wants to create a new skill, understand skill frontmatter, configure allowed-tools, choose skill locations, or learn best practices for writing SKILL.md files.

- **Type:** Skill
- **Install:** `agentstack add skill-trsdn-github-copilot-cli-copilot-skill-builder`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [trsdn](https://agentstack.voostack.com/s/trsdn)
- **Installs:** 0
- **Category:** [Developer Tools](https://agentstack.voostack.com/c/developer-tools)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [trsdn](https://github.com/trsdn)
- **Source:** https://github.com/trsdn/github-copilot-cli/tree/main/packages/copilot-skill-builder/skills/copilot-skill-builder

## Install

```sh
agentstack add skill-trsdn-github-copilot-cli-copilot-skill-builder
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Skill Builder

This skill helps you create well-structured Agent Skills for GitHub Copilot CLI.

## When to use this skill

- User wants to create a new Agent Skill
- User asks about the SKILL.md format or best practices
- User wants to understand how skills work in Copilot CLI
- User needs to debug or improve an existing skill

## SKILL.md Format

Every skill lives in its own directory and must contain a `SKILL.md` file:

```
.github/skills//
├── SKILL.md          # Required: skill instructions
├── scripts/          # Optional: helper scripts
├── examples/         # Optional: example files
└── templates/        # Optional: template files
```

### SKILL.md Structure

```markdown
---
name: skill-name
description: What the skill does and when Copilot should use it. Be specific to help Copilot decide when to load this skill.
license: MIT
allowed-tools: read, grep
user-invocable: true
disable-model-invocation: false
---

# Skill Title

Overview of what this skill accomplishes.

## When to use this skill

- Specific trigger 1
- Specific trigger 2

## Step-by-step procedure

1. First step
2. Second step

## Examples

### Example 1: Description
...

## References

- [Link to relevant docs](https://...)
```

### Frontmatter Fields

| Field | Required | Description |
|-------|----------|-------------|
| `name` | ✅ Yes | Unique identifier, lowercase with hyphens, max 64 chars |
| `description` | ✅ Yes | What it does and when to use it, max 1024 chars |
| `license` | ❌ No | License information for the skill |
| `allowed-tools` | ❌ No | Comma-separated string or YAML array of tools to allow when active |
| `user-invocable` | ❌ No | Whether users can invoke the skill with `/skill-name`; defaults to true |
| `disable-model-invocation` | ❌ No | Prevents automatic model invocation; defaults to false |

## Skill Locations

| Type | Location | Scope |
|------|----------|-------|
| Project skills | `.github/skills//SKILL.md` | Current repository |
| Project skills | `.agents/skills//SKILL.md` | Current repository, cross-agent standard |
| Project skills | `.claude/skills//SKILL.md` | Current repository, Claude-compatible |
| Personal skills | `~/.copilot/skills//SKILL.md` | All your projects |
| Personal skills | `~/.agents/skills//SKILL.md` | Shared across agent tools |
| Custom locations | `COPILOT_SKILLS_DIRS` | Additional comma-separated directories |
| Plugin skills | `/skills//SKILL.md` | Installed plugin scope |

## Best Practices

### Writing effective descriptions

The `description` field is critical — it's how Copilot decides when to load your skill.

**Good descriptions:**

- "Guide for debugging failing GitHub Actions workflows. Use when asked to debug CI failures."
- "Convert images between formats using ImageMagick. Use when asked to convert, resize, or optimize images."

**Bad descriptions:**

- "A useful skill" (too vague)
- "Helps with stuff" (non-specific)

### Writing effective instructions

1. **Be specific** — provide concrete steps, not vague guidance
2. **Include examples** — show expected input/output pairs
3. **Reference resources** — link to scripts and files using relative paths (e.g., `[template](./template.js)`)
4. **Define scope** — clearly state what the skill does and doesn't do
5. **Keep it focused** — one skill per concern, not a kitchen sink

### Including scripts and resources

Skills can include additional files that Copilot can reference:

```markdown
When creating a new component, use the template at [component-template](./templates/component.tsx)
as a starting point.

To run validation, execute the script at [validate](./scripts/validate.sh).
```

Only use `allowed-tools: shell` or `allowed-tools: bash` for skills and scripts you fully trust. When in doubt,
omit shell tools so Copilot asks before running commands.

## Managing Skills in Copilot CLI

```bash
/skills list     # List available skills
/skills          # Toggle skills on/off interactively
/skills info     # View details about a skill
/skills reload   # Reload after adding new skills
/skills add      # Add alternative skill location
/skills remove   # Remove a skill directory
```

## Skills vs Custom Instructions

| Aspect | Skills | Custom Instructions |
|--------|--------|-------------------|
| When loaded | On-demand, when relevant | Always, automatically |
| Scope | Task-specific | General/project-wide |
| Can include scripts | ✅ Yes | ❌ No |
| Best for | Detailed task procedures | Coding standards, conventions |

**Rule of thumb:** Use instructions for "always apply" rules, skills for "when relevant" procedures.

## Template

Use [skill-template.md](./skill-template.md) as a starting point for new skills.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [trsdn](https://github.com/trsdn)
- **Source:** [trsdn/github-copilot-cli](https://github.com/trsdn/github-copilot-cli)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-trsdn-github-copilot-cli-copilot-skill-builder
- Seller: https://agentstack.voostack.com/s/trsdn
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.