Creating Agent Skills

What it does

When your agent uses it

• Working with SKILL.md files
• Authoring new skills
• Improving existing skills
• Understanding skill structure and best practices

Example prompts

• “/creating-agent-skills”

Requirements

• Python 3

Workflow steps

7 steps, taken from the step headings in SKILL.md.

1. 1Skills Are Prompts
2. 2Standard Markdown Format
3. 3Progressive Disclosure
4. 4Effective Descriptions
5. 5Choose Type
6. 6Create SKILL.md
7. 7Add Scripts (If Needed)

What it can do on your machine

Read from SKILL.md and the folder at commit 227f78e. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown and yaml).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • code.claude.com
  • platform.claude.com
  • github.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Creating Agent Skills loads about 1.7k tokens when it runs, and up to ~30k if it reads all its reference files. Until then it costs about 58 tokens; SKILL.md has 428 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~58

When it runs · the whole SKILL.md, loaded when a task matches

~1.7k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~30k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from davekilleen/Dex at commit 227f78e, republished under its MIT licence (© davekilleen). 428 words, ~1,692 tokens.

name

creating-agent-skills

description

Expert guidance for creating, writing, and refining Claude Code Skills. Use when working with SKILL.md files, authoring new skills, improving existing skills, or understanding skill structure and best practices.

---
name: my-skill-name
description: What it does and when to use it
---

# My Skill Name

## Quick Start
Immediate actionable guidance...

## Instructions
Step-by-step procedures...

## Examples
Concrete usage examples...

my-skill/
├── SKILL.md              # Entry point (required)
├── reference.md          # Detailed docs (loaded when needed)
├── examples.md           # Usage examples
└── scripts/              # Utility scripts (executed, not loaded)

description: Extracts text and tables from PDF files, fills forms, merges documents. Use when working with PDF files or when the user mentions PDFs, forms, or document extraction.

description: Helps with documents

# Skill Name

## Quick Start
Fastest path to value...

## Instructions
Core guidance Claude follows...

## Examples
Input/output pairs showing expected behavior...

## Advanced Features
Additional capabilities (link to reference files)...

## Guidelines
Rules and constraints...

---
name: your-skill-name
description: [What it does]. Use when [trigger conditions].
---

# Your Skill Name

## Quick Start

[Immediate actionable example]

```[language]
[Code example]

[result]

### Step 3: Add Reference Files (If Needed)

Link from SKILL.md to detailed content:

```markdown
For API reference, see [REFERENCE.md](REFERENCE.md).
For form filling guide, see [FORMS.md](FORMS.md).

## Utility Scripts

Extract fields:
```bash
python scripts/analyze.py input.pdf > fields.json

### Step 5: Test With Real Usage

1. Test with actual tasks, not test scenarios
2. Observe where Claude struggles
3. Refine based on real behavior
4. Test with Haiku, Sonnet, and Opus

## Auditing Existing Skills

Check against this rubric:

- [ ] Valid YAML frontmatter (name + description)
- [ ] Description includes trigger keywords
- [ ] Uses standard markdown headings (not XML tags)
- [ ] SKILL.md under 500 lines
- [ ] References one level deep
- [ ] Examples are concrete, not abstract
- [ ] Consistent terminology
- [ ] No time-sensitive information
- [ ] Scripts handle errors explicitly

## Common Patterns

### Template Pattern

Provide output templates for consistent results:

```markdown
## Report Template

```markdown
# [Analysis Title]

## Executive Summary
[One paragraph overview]

## Key Findings
- Finding 1
- Finding 2

## Recommendations
1. [Action item]
2. [Action item]

### Workflow Pattern

For complex multi-step tasks:

```markdown
## Migration Workflow

Copy this checklist:

**Step 1: Backup database**
Run: `./scripts/backup.sh`
...

## Choose Your Approach

**Creating new content?** Follow "Creation workflow" below.
**Editing existing?** Follow "Editing workflow" below.

© davekilleen, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 25 other files (references) in .claude/plugins/compound-engineering/skills/create-agent-skills of davekilleen/Dex.

• SKILL.md
• references/api-security.md
• references/be-clear-and-direct.md
• references/best-practices.md
• references/common-patterns.md
• references/core-principles.md
• references/executable-code.md
• references/iteration-and-testing.md
• references/official-spec.md
• references/recommended-structure.md
• references/skill-structure.md
• references/using-scripts.md
• references/using-templates.md
• references/workflows-and-validation.md
• templates/router-skill.md
• templates/simple-skill.md
• workflows/add-reference.md
• workflows/add-script.md
• … and 8 more

Open the folder on GitHubat commit 227f78e

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in davekilleen/Dex, which our catalogue first saw on October 7, 2026.

• NeverSight/learn-skills.devdata/skills-md/8b-is/8b-is-mp/creating-agent-skills