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Notes/Agent Skills: Giving Claude Persistent, Portable Capabilities
Agent Skills

Agent Skills: Giving Claude Persistent, Portable Capabilities

Agent Skills let you package reusable instructions, scripts, and resources into a directory that Claude loads automatically — across Claude.ai, Claude Code, and the API.

What changed

Anthropic introduced Agent Skills as a way to extend agent behavior beyond what fits in a system prompt. A skill is a directory containing a SKILL.md file with YAML frontmatter (at minimum: name and description), plus any supporting files, scripts, or templates. Skills are supported across Claude.ai, Claude Code, the Claude Agent SDK, and the Claude Developer Platform. Skills can be installed via plugins from the anthropics/skills marketplace or built locally in .claude/skills/. As of 2026, skills and slash commands are unified — every skill automatically gets a /skill-name interface.

Why it matters

Skills solve the 'context stuffing' problem. Instead of pasting long instructions into every conversation, you package them once and Claude loads them when relevant. This enables a library of reusable agent behaviors that can be shared across projects and teams. The slash command integration makes skills feel native to the Claude Code workflow, not bolted on.

What can be built

  • PR description generator (reads git diff, outputs structured PR body)
  • Code review checklist enforcer (applies project-specific review criteria per language)
  • Documentation generator (reads TypeScript types and produces MDX-formatted API docs)
  • Commit message formatter following your team's conventional commits convention
  • Test scaffold generator (reads a function signature and produces Jest/Vitest test stubs)
  • Shared skill libraries published to GitHub for team or community reuse

Limitations & risks

  • Skills are loaded by file path — no versioning or dependency resolution built in yet
  • SKILL.md context contributes to token usage; very long skills can impact cost
  • The anthropics/skills marketplace is community-maintained — review skills before installing
  • Skills that invoke shell scripts require careful permission configuration in Claude Code
  • Cross-platform compatibility of helper scripts in skills is the author's responsibility

References

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