Back to blog
February 23, 202610 min read

Claude Code Skills: The Complete Guide

Claude Code is Anthropic's AI coding agent that lives in your terminal. It can read your codebase, write code, run commands, and manage git workflows. But its real power comes from skills — reusable instruction sets that tell Claude Code exactly how to handle specific tasks.

This guide covers everything you need to know about Claude Code skills: what they are, how to create them, and how to manage them at scale with SkillReg.

What Are Claude Code Skills?

A Claude Code skill is a structured set of instructions — defined in a SKILL.md file — that teaches the agent how to perform a specific task. Think of it as a recipe that Claude Code follows when you invoke it.

Skills can cover anything:

Without skills, every developer prompts Claude Code differently. With skills, your entire team gets consistent, repeatable results.

How Claude Code Reads Skills

When Claude Code starts a session, it looks for skill files in several locations:

  1. Project-level — .claude/skills/ in your repository root
  2. User-level — ~/.claude/skills/ for personal skills
  3. Registry — Skills pulled from SkillReg with skillreg pull

Claude Code parses the SKILL.md frontmatter to understand metadata (name, version, compatibility) and reads the body for instructions. The agent then incorporates these instructions into its context when performing related tasks.

Creating Your First Skill

Here's a complete example of a deployment skill for Claude Code:

---
name: deploy-nextjs-vercel
version: 1.0.0
description: Deploy a Next.js application to Vercel with pre-flight checks
agents:
  - claude-code
tags:
  - deployment
  - vercel
  - nextjs
---

## Overview
Deploy the current Next.js project to Vercel after running all safety checks.

## Prerequisites
- Vercel CLI installed (`npx vercel --version`)
- Project linked to Vercel (`vercel link`)
- All tests passing

## Steps
1. Run `npm run build` to verify the build succeeds
2. Run `npm test` to ensure all tests pass
3. Check for uncommitted changes with `git status`
4. If on main branch, run `vercel --prod`
5. If on feature branch, run `vercel` (preview deployment)
6. Report the deployment URL

## Guardrails
- NEVER deploy if tests are failing
- NEVER deploy with uncommitted changes
- NEVER use --force flag
- ALWAYS confirm with the user before production deployments

Skill Design Best Practices

Be Specific, Not Generic

Bad: "Review the code for issues"

Good: "Check all changed files for SQL injection vulnerabilities by looking for string concatenation in database queries. Flag any query that doesn't use parameterized statements."

Define Clear Guardrails

Guardrails are the most important part of a production skill. They prevent the agent from taking destructive or unauthorized actions.

Every skill should explicitly state:

Use Semantic Versioning

When you update a skill, bump the version:

Keep Skills Focused

One skill should do one thing well. A "deploy-and-test-and-review" skill is three skills pretending to be one. Split them up and compose them when needed.

Managing Skills Across a Team

When you have 5 developers, copy-pasting SKILL.md files works. When you have 50, it doesn't. This is where a registry becomes essential.

The Problem

The Solution: SkillReg

SkillReg gives you a central registry for all your team's skills:

# Publish a skill
skillreg push @your-org/deploy-nextjs-vercel

# Install it on another machine
skillreg pull @your-org/deploy-nextjs-vercel

# Pin to a specific version
skillreg pull @your-org/deploy-nextjs-vercel@1.2.0

Every developer gets the same skill. Updates propagate through version bumps. Security scans run on every publish.

Advanced Patterns

Environment-Aware Skills

Skills can declare required environment variables:

env:
  VERCEL_TOKEN:
    description: "Vercel API token for deployments"
    required: true
  SLACK_WEBHOOK:
    description: "Slack webhook for deployment notifications"
    required: false

Claude Code will check for these variables before executing and warn if any are missing.

Composable Skills

Reference other skills to build complex workflows:

## Steps
1. Run the `lint-check` skill to verify code quality
2. Run the `security-scan` skill to check for vulnerabilities
3. Run the `deploy-staging` skill to deploy to staging
4. Wait for user confirmation
5. Run the `deploy-production` skill

Conditional Logic

Skills can include conditional steps:

## Steps
1. Check the current branch name
2. If on `main`:
   - Run the full test suite
   - Deploy to production
3. If on a feature branch:
   - Run only affected tests
   - Deploy to preview environment

Claude Code vs Other Agents

While this guide focuses on Claude Code, the SKILL.md format is agent-agnostic. The same skill file works across multiple agents:

| Feature | Claude Code | Codex | Cursor | |---------|-------------|-------|--------| | SKILL.md support | Native | Via plugin | Via extension | | Guardrail enforcement | Strong | Moderate | Basic | | Environment variables | Full support | Partial | Partial | | Registry integration | SkillReg CLI | SkillReg CLI | Manual |

Getting Started

  1. Install the SkillReg CLI (2 minutes)
  2. Create your first SKILL.md using the format spec
  3. Push it to the registry with skillreg push
  4. Share it with your team and start getting consistent results

Skills turn Claude Code from a general-purpose assistant into a specialized tool that knows your team's exact workflows. The investment in writing good skills pays for itself on the first day.