Anthropic Agent Skills

Agent Skills are Anthropic's format for packaging expertise an agent can load on demand: each skill is a folder with a SKILL.md (YAML frontmatter plus Markdown instructions) and optional scripts, references, and examples. When the agent's task matches a skill's description, the skill content is injected into context — no fine-tuning, no prompt bloat for everything else.

The anthropics/skills repo is the official collection, and at 181,000+ stars it has become the de facto standard: document skills (DOCX, PDF, PPTX, XLSX), creative and enterprise skills, plus example skills, all installable in Claude Code via the anthropic-agent-skills marketplace. The format itself is open (agentskills.io hosts the spec) and third-party harnesses — OpenCode, Codex, community CLIs — have adopted it. Two caveats: individual skills carry their own licenses, so check before redistributing, and the install path is smoothest inside Anthropic's own tooling.

1. In Claude Code, add the marketplace: /plugin marketplace add anthropics/skills.
2. Install a plugin, e.g. /plugin install document-skills@anthropic-agent-skills for the DOCX/PDF/PPTX/XLSX skills.
3. The agent now loads matching skills automatically when relevant to the task.
4. For the API: create skills via the Skills API (see the Skills API quickstart in the Anthropic docs) and reference them in requests.
5. To author your own: write a SKILL.md with name/description frontmatter, add optional scripts and references, and validate with the skills-ref tool.