skill

A skill is a packaged set of written instructions that an AI agent loads when a task calls for a particular kind of know-how, such as following a release checklist or filling in a document template. In the common format, each skill is a folder containing a SKILL.md file with a short name and description followed by the instructions. The folder can also hold scripts, reference documents, and other assets that the instructions point to.

Skills rely on progressive disclosure. At startup, an agent sees only each skill’s name and description, which costs few tokens. It reads the full instructions only when a request matches, which keeps the context window free for the task at hand.

Anthropic introduced the format for Claude in October 2025 and published it as the open Agent Skills standard in December 2025. Tools such as Claude Code and Codex CLI now support it.

A person and a robot beside a filing cabinet with drawers labeled GLOBAL, PROJECT, and LOCAL, next to a Python logo, a CLAUDE.md tag, and a screen labeled MEMORY with checklist items.

Tutorial

How to Write a CLAUDE.md File for Claude Code

Learn how to write a CLAUDE.md file for Claude Code, with global, project, and local examples that capture your Python commands and conventions.

intermediate ai tools

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By Sarah Jane Ross • Updated Oct. 12, 2026
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