Definition
Agent Skills are an open standard for giving AI agents specialized knowledge. A skill is a folder with a SKILL.md file that teaches an agent a specific task or domain, plus any scripts or reference material it needs. Anthropic developed skills while working on Claude Code and published the standard in December 2025. On October 22, 2026, it donated the standard to the Agentic AI Foundation under the Linux Foundation, the same group that now hosts the Model Context Protocol.
The specification is short. SKILL.md starts with YAML frontmatter that requires a name (up to 64 characters, lowercase letters, numbers and hyphens, matching the folder name) and a description (up to 1,024 characters) saying what the skill does and when to use it. The Markdown body holds the instructions. Optional scripts, references and assets folders can sit alongside it.
Skills use progressive disclosure to save context. At startup an agent loads only each skill's name and description, roughly 100 tokens. The full SKILL.md is read when the skill is activated, and the spec recommends keeping it under 5,000 tokens. Files in other folders load only if the task needs them. This keeps a large library of skills from filling the model's context window, which is a core concern of context engineering.
Skills sit next to other agent instruction formats. An AGENTS.md file holds standing project guidance for AI agents, while a skill holds a procedure the agent loads on demand. MCP connects an agent to external tools and data, and a skill can tell the agent how to use them. Anthropic reports more than 70 agent platforms, including ChatGPT, Cursor, GitHub Copilot and VS Code, have integrated skills, with 1 million skills published and nearly 280 million installs.
For marketers and site owners, skills matter in two ways. Cloudflare's agent readiness score counts an Agent Skills index as a capability, so publishing one is a way for a site to teach agents how to use it. They also shape what coding agents do, which is the subject of coding agent visibility. Our Promptwatch MCP guide shows one way to connect tools to an agent.
Examples of Agent Skills (SKILL.md)
- A developer adds a pdf-processing skill folder to a repo, and the agent loads it only when a task mentions PDFs.
- A SaaS company ships a skill that explains its API conventions, so coding agents write correct calls without the developer pasting docs.
- A marketing team keeps a brand-voice skill with a style guide, and its agent loads the full guide only when drafting copy.
- A documentation site publishes an agent skills index at a well-known path, so agents know how to use its tools.
