Skills teach an agent how you work.
A skill is just a folder with instructions (and sometimes scripts) that an AI agent loads when a task matches. "Make our quarterly report", "write a proposal in our format", "test this web app": each can be a skill.
Only the label is read until needed.
The agent sees names and descriptions
Of every installed skill. That's a few lines each, so 100 skills barely cost anything.
A task matches a description
You say "turn this into a spreadsheet", it matches the
xlsxskill, and only then the fullSKILL.mdgets loaded.It follows the recipe
Instructions, templates, and scripts in the folder. Same result every time, in your style.
Skills are an open standard: the same folder works in Claude (app, Code, API), ChatGPT and Codex, Cursor and others.
quarterly-report/
├── SKILL.md ← required
├── scripts/ ← optional code
└── templates/ ← optional files
---
name: quarterly-report
description: Builds the quarterly report from the
sales export. Use when asked for a "quarterly
report", "Q3 numbers" or "board update".
---
1. Ask for the sales CSV if it isn't attached.
2. Run scripts/summarize.py on it.
3. Fill templates/report.docx, keep our fonts.
4. End with 3 bullet risks, no fluff.Skill vs MCP vs plugin vs prompt
| Thing | What it is | Example |
|---|---|---|
| Prompt | A one-off instruction in the chat. | "Translate this to Spanish." |
| Project / Custom GPT | Standing instructions and files for one chat space. | "Company assistant" with uploaded handbook |
| Skill | Know-how: how to do a job. Loaded only when relevant. | How we write a sales proposal |
| MCP server | Access: tools and data from another system. | Read Gmail, write to Notion, drive a browser |
| Plugin | An installable bundle: skills + MCP servers + commands together. | /plugin install document-skills@anthropic-agent-skills |
| Agent / subagent | An AI that works through several steps with tools on its own. | Claude Code, Codex, ChatGPT agent |
MCP gives hands, skills give know-how. The best setups use both: a Notion MCP server plus a skill that says how your team writes meeting notes.
Adding a skill, per app
Claude Code
terminalOfficial skills come as plugins:
/plugin marketplace add anthropics/skills
/plugin install document-skills@anthropic-agent-skillsYour own skill: drop the folder in ~/.claude/skills/ (every project) or .claude/skills/ (this project).
claude.ai & desktop
appAnthropic's example skills are already built in on paid plans. For your own: Settings → Capabilities → Skills, upload the folder as a .zip.
Codex
terminal$skill-installer playwrightOr put the folder in .agents/skills/. List them with /skills, restart Codex after installing. New official examples live in openai/plugins.
ChatGPT
appMention a skill with @name, or it kicks in when your request matches its description. Make one with @skill-creator.
SKILL.md and scripts/ folder on GitHub and skim what it does. How to judge a repo →Skills worth your time
Every skill and skill pack we list, with what it's for and how to install it, lives in the tool finder.
Browse skills