Claude Skills & the Ecosystem

Reusable, contextually-loaded instruction packs. The 2026 evolution of "system prompt" without the bloat.

Markdown File

200-400

Lines Max

On-demand

Loaded Contextually

Marketplaces

Skills vs MCP vs Agents — the three primitives

MCP servers

Provide capabilities — tools the agent can call (filesystem, GitHub, Slack…).

THIS POST

Skills

Provide knowledge + instructions — how to behave in specific contexts.

Subagents

Provide specialized personas — model + tools + system prompt for a recurring role.

Anatomy of a skill (.claude/skills/<name>.md)

# Skill: Swift Refactor Specialist

## Description
Specializes in modernizing Swift / SwiftUI per 2026 conventions.

## When to Use
User says "refactor" · NavigationView → NavigationStack · iOS 17+ targets

## Instructions
1. Read target file(s) first
2. Prefer SwiftUI over UIKit
3. Run tests after refactor
4. Update CLAUDE.md decisions log

Why Skills Beat System Prompt Stuffing

Skills load contextually. Tiny index always present; full skill loads only when description matches. No more 5000-line system prompt with conflicting rules competing for attention.

First Skill to Write

The repeated instruction. If you've told Claude the same thing 3× across sessions, externalize it.

Where skills live

Skill patterns that work

anthropics/skills
Official reference. Browse first.
agentskills.io
Community directory. Categorized.
skillsmp.com
Marketplace. Free + premium.
Your repo's .claude/skills/
Project-specific.
~/.claude/skills/
Personal, all projects.

Domain-specific
"Stripe API Patterns" · "RDR2 Lore"
Process skills
"Pre-commit Reviewer" · "PR Writer"
Style skills
"djEnterprises Voice"
Safety skills
"Pre-Deploy Guard" · "DB Migration Check"