Claude Skills are awesome, maybe a bigger deal than MCP
TL;DR Highlight
Anthropic's Claude Skills bundles markdown files and scripts to give LLMs new capabilities.
Who Should Read
Developers who use Claude via API or Claude.ai and want a structured way to add reusable capabilities to their LLM workflows.
Core Mechanics
- A Skill is a directory containing a SKILL.md instruction file and optional supporting scripts/resources
- Skills are loaded at conversation start and persist for the session
- Multiple skills can be combined in a single session for composable functionality
- Reduces repetitive prompt engineering by packaging common workflows as reusable units
- Anthropic provides a skill registry and tooling for creating/sharing skills
Evidence
- Official Anthropic announcement and documentation
- Community demonstrations showing skills enabling consistent multi-step workflows
- Comparison with raw system prompts shows reduced token usage and higher reliability
How to Apply
- Start by converting your most frequently repeated system prompts into skill packages.
- Include example inputs and outputs in SKILL.md to guide the LLM's behavior more precisely.
- Version control your skills folder alongside your code for reproducibility.
Code Example
snippet
# Example skill directory structure
# my-skill/
# SKILL.md <- Description and trigger conditions in frontmatter
# core/
# helper.py <- Utilities the model can call
# templates/
# boilerplate.py <- Template files
# SKILL.md frontmatter example:
# ---
# description: "Toolkit for creating animated GIFs optimized for Slack"
# trigger: "users request animated GIFs or emoji animations for Slack"
# ---
# Pattern used in Python within a skill:
import sys
sys.path.insert(0, '/mnt/skills/examples/slack-gif-creator')
from core.gif_builder import GIFBuilder
# Validate Slack size limit after GIF creation
passes, info = check_slack_size('output.gif', is_emoji=False)
if not passes:
print(f"⚠ {info['size_kb']:.1f}KB > {info['limit_kb']}KB limit")Terminology
Skill PackageA folder containing a markdown instruction file and optional scripts/resources that defines a reusable LLM capability.
SKILL.mdThe primary instruction file in a Claude Skill, written in markdown, describing what the skill does and how to use it.
Session ContextThe accumulated conversation history and loaded resources available to the LLM within a single conversation.