Agent Skills

📖 2 min read claudeagent-skillsclaude-codemcp

How agent skills work in the Claude ecosystem — the SKILL.md open standard, project-level vs user-level skills, sub-agents, and how skills differ from MCP and tools.

Key Takeaways

Agent Skills teach Claude Code how to approach specific tasks — packaged as SKILL.md markdown files
Skills are playbooks (process knowledge) — MCP servers are verbs (live data/actions)
32+ tools support the SKILL.md standard, including VS Code, Copilot, Cursor, and Gemini CLI

This is a Claude-specific overview. For the complete deep-dive — including the SKILL.md format, skills vs tools vs MCP, sub-agent orchestration, and the full ecosystem — see Agent Skills — Full Deep Dive.

What Are Agent Skills?

An agent skill is a packaged set of instructions that teaches Claude Code how to approach a specific kind of task. Write a SKILL.md file, place it in .claude/skills/, and every developer on your team automatically gets the same workflow.

Skills started inside Claude Code (October 2025) and became an open standard by Anthropic (December 2025). Within 48 hours, Microsoft integrated it into VS Code and Copilot. OpenAI added it to Codex CLI and ChatGPT. By early 2026, 32+ tools support the same SKILL.md format.

Quick Setup (Claude Code)

# Project-level skills (shared via git)
.claude/skills/
  generate-migration/
    SKILL.md

# User-level skills (your machine only)
~/.claude/skills/
  my-custom-workflow/
    SKILL.md

Minimal SKILL.md:

---
name: generate-migration
description: Generate database migration files for schema changes
---

## Process
1. Read the schema change request
2. Check existing migrations for naming convention
3. Generate the up/down migration files
4. Run `npm run migrate:check` to validate
5. Commit with message: "migration: {description}"

Skills vs MCP — When to Use Which

Use a Skill when…	Use MCP when…
You have a repeatable process	You need live data (database, API)
Knowledge is stable for weeks	State changes per request
The task involves judgment calls	The task is deterministic
You want a playbook, not an API	You want a data connector

They work best together. A “Comparable Company Analysis” skill defines the methodology — which metrics matter, the output format. An MCP server fetches live financial data. The skill orchestrates; the MCP delivers.

Going Deeper

The full Agent Skills deep dive covers:

The complete SKILL.md format with all sections
Advanced examples with scripts and assets
Sub-agents and orchestration patterns
When to use skills vs tools vs MCP
The ecosystem of 32+ supporting tools