What AI Skills are — and how to build your own (with 4 ready-made skills to download)

Every week someone asks me what those "skills" I keep mentioning actually are. Short answer: it's the simplest way to teach an AI a new trick — and have it repeat that trick the same way, every time. I use skills every day in Claude Code, from how I write a commit to how I review PHP security. No fluff: here's what they are, what they're for, what that SKILL.md file is, and how to build your own — plus 4 ready-made skills to download at the end.

What AI Skills are

Think of a skill as a recipe you hand to the AI: a set of instructions (and, optionally, scripts and supporting files) that teaches the model to do a specific task your way. Instead of re-explaining everything each conversation, you store that knowledge once — and the AI pulls it in on its own when the task shows up.

Agent Skills are an open standard from Anthropic (the company behind Claude). The nice part: the same skill works in Claude on the web, in Claude Code (terminal), and via the API. And it's just text — no SDK or framework to install.

What they're for (in practice)

• Standardize: the AI follows your conventions (commits, reviews, writing tone) without you repeating yourself.
• Save time and context: the knowledge is stored; you don't paste the same instructions every single time.
• Share: version it in Git and hand it to your team — everyone gets the same built-in "expert".
• Compose: several small, focused skills beat one giant, confusing prompt.

What the SKILL.md file is

Every skill is a folder with at least one file called SKILL.md. It has two parts:

1. A YAML frontmatter at the top (between ---) with two required fields:
   • name — the identifier, lowercase with hyphens (e.g. commit-craft);
   • description — what the skill does and when to use it. That sentence is how the model decides, on its own, to trigger the skill.
2. The Markdown body: the instructions themselves — the step-by-step the AI should follow.

A minimal SKILL.md:

---
name: commit-craft
description: Use when writing commit messages from a diff.
---

# Commit Craft
You write commit messages in the Conventional Commits format...

The golden tip: nail the description. It's what makes the model remember to use the skill at the right moment. A vague description = a skill that never fires.

How to build your own skill, step by step

1. Create a folder named after the skill (e.g. commit-craft/).
2. Inside it, create SKILL.md with the frontmatter (name, description) and a body with the instructions.
3. (Optional) Bundle scripts, examples or reference files in the same folder — the AI can run or consult them.
4. Keep SKILL.md lean (Anthropic recommends under ~500 lines). A focused skill > a skill that tries to do everything.
5. Install it: in Claude Code, drop the folder into ~/.claude/skills/ (or your project's skills directory). Done — Claude now considers the skill whenever the description matches the task.

In Claude Code you can also install official skills via Anthropic's plugin marketplace (anthropics/skills), which auto-update. But the real fun is building your own, in your own style.

The killer move: 4 ready-made skills to download

So you don't start from scratch, I left you 4 generic, useful skills. Download, unzip the folder into ~/.claude/skills/, and use it today:

Grab all 4 at once (bundle)

Each .zip holds the skill folder with its SKILL.md. Open it and read — it's plain text, easy to adapt to your taste in 2 minutes.

In short

A skill = a folder + a SKILL.md with name, description and instructions. It's the cleanest way to turn "the way you do things" into something the AI repeats on its own, the same way every time. Start with one of these 4, edit it, and soon you'll have a pocket team of experts.

I want to automate the way I work

That's exactly what I do for businesses: take the repetitive task off people's plates — with AI, automation and custom code. If that fits your case, let's talk.