What are Claude Skills?

Claude Skills — also called Agent Skills — are Claude’s mechanism for reusable know-how. Each Skill is a plain folder with a SKILL.md file that describes a procedure: how your team reviews code, how release notes are written, which brand voice to use. Supporting scripts, templates, and reference files can live in the same folder.

The design principle is progressive disclosure. At the start of a session Claude keeps only each Skill’s name and description in mind. When a request matches a description, the full instructions are loaded for that conversation. A library of dozens of Skills therefore costs almost nothing until one of them is actually used.

How a Skill is structured

my-skill/
├── SKILL.md        # frontmatter + instructions
├── templates/
│   └── issue.md    # optional supporting files
└── scripts/
    └── collect_prs.sh

The frontmatter carries the activation trigger: name identifies the Skill and description explains when to use it. The body is plain Markdown for Claude to follow, and supporting files are referenced by relative path.

Where Skills live

Personal Skills go in ~/.claude/skills, project Skills in .claude/skills inside the repository, and plugin Skills arrive through a plugin marketplace via the /plugin command. The same Skill format also works across agents: Codex and Gemini CLI read Skills from their own directories, so one capability often needs several installed copies.

Skills vs. MCP servers, plugins, and slash commands

• MCP servers connect Claude to external systems and tools; Skills package instructions and files. They compose well together: a Skill describes the workflow, an MCP server provides the connection.
• Plugins are distribution bundles that can include Skills; installing a plugin from a marketplace is one way to add Skills.
• Slash commands are single shortcuts you type in a session; a Skill is a described capability Claude can choose on its own when the task fits.

What Skills are good at

• Repeatable team procedures: code-review checklists, release processes, incident reports.
• Project conventions: brand voice, API guidelines, architecture rules that should shape every change.
• Domain workflows: documentation generation, data analysis routines, QA checklists with project-specific steps.

Getting Skills

You can write a Skill yourself — any folder with a valid SKILL.md qualifies — copy one from a GitHub repository, or browse a marketplace. SkillSlot, a local-first macOS app, includes a Skill market that searches third-party sources such as ClawHub and installs what you find into one organized Vault.

When one Skill becomes thirty

The format is so lightweight that collections grow fast. A few Skills are easy to hand-manage; past that, the questions change from “how do I write one” to “which copy is current, and which agent has it”. SkillSlot answers those with a single Vault, AI-assisted summaries, reusable Loadouts, and explicit deployment to Claude Code, Codex, and Gemini CLI — so the collection stays understandable as it grows.