Anthropic Official Skills: Complete Guide to 17 Open-Source Agent Skills

Anthropic has open-sourced 17 Agent Skills at anthropics/skills, covering creative design, document creation, technical development, and enterprise communication. These skills work across Claude.ai, Claude Code, and the Claude API. This guide provides a deep dive into every skill.

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What Are Agent Skills?

Skills are folders of instructions, scripts, and resources that Claude loads dynamically to improve performance on specialized tasks. Each skill’s core is a SKILL.md file with YAML frontmatter and markdown instructions.

---
name: my-skill-name
description: What this skill does and when to use it
---

# My Skill Name
[Instructions Claude will follow]

Installation

Claude Code:

/plugin marketplace add anthropics/skills
/plugin install document-skills@anthropic-agent-skills
/plugin install example-skills@anthropic-agent-skills

Claude.ai: All skills are built-in for paid plans.

Claude API: See the Skills API Quickstart.

Skill Loading (Progressive Disclosure)

1. Metadata — Always visible (~100 word description)
2. SKILL.md — Loaded on trigger (<500 lines)
3. References — Loaded on demand (scripts, data, templates)

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All 17 Skills at a Glance

Category	Skill	Purpose
Creative	algorithmic-art	p5.js generative art with seeded randomness
	canvas-design	Museum/magazine-quality visual art
	slack-gif-creator	Slack-optimized animated GIFs
	theme-factory	10 professional color themes
Design	brand-guidelines	Anthropic brand identity
	frontend-design	Production-grade UI, anti-”AI slop”
	web-artifacts-builder	React + Tailwind interactive artifacts
Documents	docx	Word document creation/editing
	pdf	PDF read/create/merge/OCR/forms
	pptx	PowerPoint presentation creation
	xlsx	Excel spreadsheets with formulas
Technical	claude-api	Claude API/SDK development
	mcp-builder	MCP Server construction
	skill-creator	Skill creation with eval testing
	webapp-testing	Playwright browser automation
Enterprise	doc-coauthoring	Collaborative document writing
	internal-comms	Internal communication templates

---

Creative & Generative Skills

Algorithmic Art

Creates generative art using p5.js with seeded randomness and interactive parameter exploration.

Workflow:

1. Create Algorithmic Philosophy (.md) — define aesthetic direction
2. Implement p5.js interactive piece (.html) — using provided viewer template

Features:

• Seeded randomness for reproducibility (Art Blocks pattern)
• Interactive parameter controls and seed navigation
• Particle systems, noise fields, flow fields
• Philosophy: beauty in process, not final frame

Canvas Design

Museum/magazine-quality visual art in .png and .pdf.

• 90% visual, 10% text — text only as visual accent
• Sophisticated design-forward approach (never cartoony)
• Bundled canvas-fonts directory
• Emphasis: appears hand-made, not AI-generated

Slack GIF Creator

Animated GIFs optimized for Slack.

Spec	Value
Emoji size	128x128
Message size	480x480
FPS	10-30
Colors	48-128
Duration	<3 seconds (emoji)

Built-in: GIFBuilder class, 6 easing functions, 8 animation concepts (shake, pulse, bounce, spin, fade, slide, zoom, particle burst).

Theme Factory

10 pre-set professional themes with colors and fonts.

Themes: Ocean Depths, Sunset Boulevard, Forest Canopy, Modern Minimalist, Golden Hour, Arctic Frost, Desert Rose, Tech Innovation, Botanical Garden, Midnight Galaxy.

Each theme: complete color palette (hex codes) + complementary font pairings. Applicable to slides, docs, reports, landing pages.

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Design & Frontend Skills

Brand Guidelines

Applies Anthropic’s official brand identity. Colors: Dark #141413, Light #faf9f5, Orange #d97757, Blue #6a9bcc, Green #788c5d. Fonts: Poppins (headings), Lora (body).

Frontend Design

Production-grade frontend interfaces that avoid “AI slop” aesthetics.

Principles:

• Bold aesthetic direction — intentional extremes (minimalism or maximalism)
• Distinctive typography — never Inter/Arial/system fonts
• Cohesive palette — dominant color 60-70%, sharp accents
• Motion — CSS animations, scroll-triggering, hover states
• Spatial composition — asymmetry, overlap, diagonal flow, generous negative space

Banned: Generic backgrounds, purple gradients, uniform rounded corners, cookie-cutter patterns.

Web Artifacts Builder

Multi-component interactive artifacts using React 18 + TypeScript + Tailwind + shadcn/ui.

• 40+ pre-installed shadcn/ui components + Radix UI
• scripts/init-artifact.sh — project initialization
• scripts/bundle-artifact.sh — bundle to single self-contained HTML
• Parcel bundler with path alias configuration

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Document Skills (Source Available)

These four skills power Claude’s document capabilities. Source-available (not open source) for developer reference.

DOCX — Word Documents

Operation	Tool
Read	pandoc (text), unpack XML (raw)
Create	docx-js library
Edit	Unpack -> edit XML -> repack

Supports: tables (DXA units), images, headers/footers, tracked changes, TOC, multi-column layouts, hyperlinks, bookmarks, footnotes.

PDF — PDF Processing

Operation	Tool
Read/Extract text	pdfplumber
Extract tables	pdfplumber + pandas
Create	reportlab (Canvas or Platypus)
Merge/Split/Rotate	pypdf
OCR	pytesseract
Forms	Detailed in FORMS.md
CLI operations	qpdf

PPTX — PowerPoint

Operation	Tool
Read	markitdown (text), thumbnail.py (visual)
Create	pptxgenjs (npm)
Edit	Unpack -> edit XML -> clean -> repack

Design rules: bold palettes with 60-70% primary color, distinctive font pairings (avoid Arial), titles 36-44pt, body 14-16pt. Visual QA is mandatory — assume problems exist.

XLSX — Excel Spreadsheets

Tools: pandas (data analysis), openpyxl (complex formatting/formulas).

Critical rules:

• Use formulas (=SUM()), NEVER hardcoded values
• Run scripts/recalc.py after formula creation
• Financial model color coding: Blue (inputs), Black (formulas), Green (internal links), Red (external links)
• Validate zero formula errors (#REF!, #DIV/0!, #VALUE!, #N/A, #NAME?)

---

Technical & Development Skills

Claude API

Build LLM applications using Claude API or Anthropic SDKs.

Models:

Model	Context	Use
Opus 4.6	200K	Default, most capable
Sonnet 4.6	200K	Complex coding
Haiku 4.5	200K	Fast, low cost

Key features:

• Thinking: thinking: {type: "adaptive"} (Opus/Sonnet 4.6)
• Effort: output_config: {effort: "low"|"medium"|"high"|"max"}
• Streaming: default for long input/output
• Tool Use: automatic runner or manual loop
• Structured Outputs: output_config: {format: {...}}
• Files API: persistent file references
• SDKs: Python, TypeScript (full), Java, Go, Ruby (beta), C#, PHP, cURL

Decision tree: Single call -> Workflow (tool use) -> Agent (open-ended exploration).

MCP Builder

Create high-quality MCP (Model Context Protocol) servers.

Four phases:

1. Deep Research — API docs and integration patterns
2. Implementation — TypeScript recommended, Python alternative
3. Review/Test — MCP Inspector (npx @modelcontextprotocol/inspector)
4. Evaluations — 10 complex, independent evaluation questions

Principles: Comprehensive API coverage > workflow tools. Clear naming (github_create_issue). Actionable error messages. Tool annotations: readOnlyHint, destructiveHint, idempotentHint.

Skill Creator

Create new skills, iterate, and measure performance.

Workflow:

1. Draft SKILL.md + resources
2. Set up evals/evals.json (2-3 realistic prompts)
3. Evaluate: with-skill vs. baseline in parallel
4. Improve based on feedback
5. Expand test coverage
6. Optimize description triggering

Tools: eval-viewer/generate_review.py, run_loop.py (20-query description optimization), benchmarking (mean +/- stddev).

Webapp Testing

Test local web applications using Playwright.

• Pattern: Reconnaissance-then-action (wait networkidle -> screenshot -> identify selectors -> execute)
• scripts/with_server.py manages server lifecycle
• Supports multiple servers simultaneously (backend + frontend)
• Always wait for page.wait_for_load_state('networkidle') before DOM inspection

---

Enterprise & Communication Skills

Doc Coauthoring

Structured workflow for collaborative document creation.

Stage	Process
1. Context Gathering	User provides background, Claude asks 5-10 clarifying questions
2. Refinement	Section-by-section: brainstorm (5-20 options) -> curate -> draft -> iterate
3. Reader Testing	Fresh Claude (no context) validates document clarity

Quality gate: after 3 iterations with no changes, ask what can be removed.

Internal Comms

Company-specific internal communications using templates.

Types: 3P updates (Progress/Plans/Problems), company newsletters, FAQ responses, status reports, leadership updates, project updates, incident reports.

Each type has corresponding guidelines and templates in the examples/ directory.

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Cross-Cutting Design Patterns

1. Anti-AI-Slop — All creative skills emphasize distinctive, context-specific design over generic templates
2. Philosophy Before Implementation — Define aesthetic direction before coding
3. Formulas Over Calculations — Dynamic documents, not hardcoded values
4. Mandatory Validation — Visual QA for PPTX, zero errors for XLSX, evals for skills, 10 questions for MCP
5. Progressive Disclosure — Metadata always visible, details loaded on demand

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Building Your Own Skill

my-skill/
├── SKILL.md           # Required: instructions + frontmatter
├── references/        # Optional: reference docs
├── scripts/           # Optional: helper scripts
├── assets/            # Optional: resources
└── evals/             # Recommended: evaluation tests
    └── evals.json

Frontmatter needs only name and description. The markdown content contains instructions, examples, and guidelines.

Resources:

• GitHub Repository
• Agent Skills Specification
• Skills Documentation
• Skills API Quickstart