What are agent skills?

An agent skill is a small, focused package of instructions and supporting files that teaches a coding agent — like Anthropic's Claude Code or OpenAI's Codex — how to perform a specific task well. Instead of re-explaining "here is how we write a Helm chart" or "here is how we format a PlantUML component diagram" in every chat, you install a skill once and the agent picks it up whenever the task comes up.

How a skill is different from a plain prompt

A prompt lives inside a single conversation. It is gone when the session ends and cannot be shared reliably across projects, teammates, or agents. A skill lives on disk as a versioned bundle. It is:

• Trigger-based. Each skill declares what user requests it handles, so the agent only loads it when relevant.
• Composable. Skills ship their own references, scripts, and templates, so the agent has the right context without you pasting it in.
• Reusable. One skill works across any project that installs the same bundle.

How a skill triggers

Every skill publishes a short trigger description — a few sentences that tell the agent when to use it. When your request matches, the agent reads the skill's main instructions, pulls in any references it needs, and runs relevant scripts. You normally do not have to invoke a skill by name: just ask the agent to do the task in natural language. For example, installing the PlantUML skill means a request like "draw a sequence diagram for the login flow" starts rendering real UML instead of ASCII art.

What is a skill bundle?

Skills are small, so they are almost always shipped in bundles. A bundle groups related skills under one installable plugin. On this marketplace there are 5 bundles:

• Shared Skills — Reusable Claude Code and Codex skills for common developer workflows and shared utilities.
• CI/CD Skills — Claude Code and Codex skills focused on CI/CD pipelines, release flows, and delivery automation.
• Software Design Skills — Claude Code and Codex skills focused on software design, OOP, architecture, and maintainability guidance.
• Doc Skills — Claude Code and Codex skills for creating and editing Word, PowerPoint, Excel, and PDF documents.
• Web Design Skills — Claude Code and Codex skills for web design, UI/UX, CSS, HTML, and front-end development workflows.

You install an entire bundle at once — you do not cherry-pick individual skills. After installation every skill inside the bundle is available to the agent, and the agent picks the right one based on your request.

How installing works

In Claude Code you add this site as a marketplace, then install a bundle with/plugin install. The bundle unpacks into your Claude Code configuration and its skills become available immediately. In Codex you add the same GitHub repository as a plugin marketplace withcodex plugin marketplace add, then install bundles from the Codex plugin directory.

Visit the full skill catalog to browse everything, or read the Claude Code vs Codex comparison to see how the two platforms handle skills differently.

Want the step-by-step install flow? See the install-from-GitHub walkthrough, or browse every long-form guide in the Learn hub.

Official documentation

• Anthropic Claude Code docs: docs.claude.com
• OpenAI Codex docs: platform.openai.com/docs