Agent Skills: How markdown files are turning Claude Code into a platform

Your AI coding agent can write code. It can refactor, debug, and ship features. But can it generate a PowerPoint deck from your project data? Create a PDF report? Follow your team's React best practices without being told twice?

Until recently, the answer was no. AI coding agents were powerful but narrow - confined to reading and writing code. Skills change that.

What are agent skills?

Skills are markdown files that teach Claude Code new capabilities and domain knowledge. Unlike MCP servers, which require running infrastructure, a skill is just a .md file dropped into your project's .claude/ directory. Claude reads it at the start of every session and follows the instructions within.

The concept is deceptively simple. The implications are not.

A single skill file can teach Claude Code to:

• Generate Word documents, Excel spreadsheets, and PowerPoint presentations
• Follow your team's specific coding conventions and architectural patterns
• Run systematic debugging workflows instead of guessing
• Build data visualizations with D3.js
• Write SwiftUI code following Apple's latest design guidelines

# Install any skill with one command
npx skills add anthropics/skills/docx

That's it. One command, and your AI agent permanently gains a new capability.

The skills marketplace

We built the Skills Marketplace to make discovering and installing skills effortless. It curates skills across seven categories: Development, DevOps & Infrastructure, Security, Design & Creative, Documents, Communication, and Marketing.

The marketplace currently features skills from:

• Anthropic (official): Document manipulation (docx, pdf, pptx, xlsx), MCP builder, webapp testing, frontend design, artifacts builder, and a skill-creator skill that helps you build your own
• obra/superpowers: Jesse Vincent's popular collection including brainstorming, systematic debugging, TDD, plan execution, and parallel agent dispatching - with nearly 9,000 GitHub stars
• Vercel: React best practices, React Native patterns, and web design guidelines
• Supabase: Postgres performance optimization and best practices
• Trail of Bits: Security-focused skills for code auditing
• Remotion: Video generation skills
• Community contributors: D3.js visualizations, scientific computing, SwiftUI development, and more

Each skill card shows the description, author, GitHub stars, and a one-line install command. Click into any skill for the full documentation and setup details.

Why skills matter more than you think

They compound

Install a document skill today and every future session benefits from it. Unlike a one-off prompt, skills persist across sessions. Your agent gets smarter permanently with each skill you add.

They encode team knowledge

The most powerful skills aren't the generic ones - they're the ones your team writes. Imagine a skill that encodes your team's:

• API design conventions
• Error handling patterns
• Testing requirements
• PR review checklist
• Database migration practices

New team members (human and AI) follow the same standards from day one. The knowledge that used to live in senior engineers' heads now lives in a file that every Claude Code session reads automatically.

They're composable

Skills don't conflict. Install the Supabase Postgres skill alongside the Vercel React skill and the Anthropic testing skill. Claude Code reads all of them and applies the relevant knowledge based on context. You're building a custom AI agent tailored to your exact stack.

They work with Cyrus out of the box

When you install skills in a repository that Cyrus monitors, every issue Cyrus picks up benefits from those skills automatically. Assign a Linear issue to create a PDF report, and if the pdf skill is installed, Cyrus knows how to generate it. No additional configuration needed.

How to install skills

Installing a skill takes seconds:

# Official Anthropic skills
npx skills add anthropics/skills/docx
npx skills add anthropics/skills/pdf
npx skills add anthropics/skills/webapp-testing

# Community skills
npx skills add obra/superpowers --skill brainstorming
npx skills add obra/superpowers --skill systematic-debugging

# Third-party skills
npx skills add https://github.com/vercel-labs/agent-skills --skill react-best-practices
npx skills add https://github.com/supabase/agent-skills --skill supabase-postgres-best-practices

Each command downloads the skill's markdown file into your project's .claude/ directory. Claude Code picks it up automatically on the next session.

How to build your own skill

The barrier to creating a skill is intentionally low. A skill is a markdown file with structured instructions. Anthropic even provides a skill-creator skill that helps you write new skills:

npx skills add anthropics/skills/skill-creator

Once installed, you can ask Claude Code to help you create a skill for any workflow or domain knowledge you want to codify. The skill-creator guides the structure, ensuring your custom skill follows best practices for readability and effectiveness.

Here's the general structure of a skill file:

# My Custom Skill

## Overview
What this skill does and when to use it.

## Instructions
Step-by-step guidance for Claude Code to follow.

## Examples
Concrete examples of inputs and expected outputs.

## Constraints
What to avoid or watch out for.

The best skills are specific and opinionated. Instead of "write good tests," a strong testing skill says "use Vitest, mock external services with msw, test behavior not implementation, and maintain 80% coverage on new code."

What's next

The skills ecosystem is growing fast. We're seeing new skills published weekly from individual developers, companies, and open source projects. As more teams adopt Claude Code, the library of reusable knowledge will accelerate.

We'll continue expanding the Skills Marketplace with new categories, better discovery, and tighter integration with Cyrus workflows. If you've built a skill you think others would find useful, we'd love to feature it.