Design, create, audit, and improve Claude Agent Skills with expert-level progressive disclosure. Use when building new skills, reviewing existing skills, debugging activation failures, encoding domain expertise, designing skills for subagent consumption, or understanding platform constraints and distribution surfaces. NOT for general Claude Code features, runtime debugging, non-skill coding, or MCP server implementation.
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SKILL.md
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name
skill-architect
description
Design, create, audit, and improve Claude Agent Skills with expert-level progressive disclosure. Use when building new skills, reviewing existing skills, debugging activation failures, encoding domain expertise, designing skills for subagent consumption, or understanding platform constraints and distribution surfaces. NOT for general Claude Code features, runtime debugging, non-skill coding, or MCP server implementation.
{"category":"Productivity & Meta","tags":["architect","create-skill","improve-skill","skill-audit"],"pairs-with":[{"skill":"skill-creator","reason":"The architect designs skill structure; the creator guides implementation following those patterns"},{"skill":"skill-grader","reason":"Grading feedback identifies architectural weaknesses that the architect addresses"},{"skill":"skill-documentarian","reason":"Documentation standards complement architectural design for complete skill delivery"}]}
Skill Architect: The Authoritative Meta-Skill
The unified authority for creating expert-level Agent Skills. Encodes the knowledge that separates a skill that merely exists from one that activates precisely, teaches efficiently, and makes users productive immediately.
Philosophy
Great skills are progressive disclosure machines. They encode real domain expertise (shibboleths), not surface instructions. They follow a three-layer architecture: lightweight metadata for discovery, lean SKILL.md for core process, and reference files for deep dives loaded only on demand.
When to Use This Skill
✅ Use for:
Creating new skills from scratch or from existing expertise
Auditing/reviewing skills for quality, activation, and progressive disclosure
Improving activation rates and reducing false positives
Template generation without real domain expertise to encode
Quick Wins (Immediate Improvements)
For existing skills, apply in priority order:
Tighten description → Follow [What] [When to use]. NOT for [Exclusions] formula
Check line count → SKILL.md must be <500 lines; move depth to /references
Add NOT clause → Prevent false activation with explicit exclusions
Add 1-2 anti-patterns → Use shibboleth template (Novice/Expert/Timeline)
Remove dead files → Delete unreferenced files in scripts/ and references/ (no phantoms)
Test activation → Write 5 queries that should trigger and 5 that shouldn't
Progressive Disclosure Architecture
Skills use three-layer loading. The runtime scans metadata at startup, loads SKILL.md on activation, and pulls reference files only when the agent decides it needs them.
Layer
Content
Size
Loading
1. Metadata
name + description in frontmatter
~100 tokens
Always in context (catalog scan)
2. SKILL.md
Core process, decision trees, brief anti-patterns
<5k tokens
On skill activation
3. References
Deep dives, examples, templates, specs
Unlimited
On-demand, per-file, only when relevant
Critical rules:
Keep SKILL.md under 500 lines. Move depth to /references.
Reference files are NOT auto-loaded. Only SKILL.md enters context on activation.
In SKILL.md, list each reference file with a 1-line description of when to consult it. This teaches the agent what's available without loading it.
Never instruct "read all reference files before starting." Instead: "Read only the files relevant to the current step."
If a reference file is large, the agent should skim headings first, then drill into the relevant section.
Frontmatter Rules
Required Fields
Key
Purpose
Constraints
name
Lowercase-hyphenated identifier
Max 64 chars, a-z/0-9/hyphens only, no "anthropic" or "claude", no XML tags
description
Activation trigger: [What] [When to use]. NOT for [Exclusions]
Max 1024 chars, no XML tags. See Description Formula
Optional Fields
Key
Purpose
Example
allowed-tools
Comma-separated tool names (least privilege)
Read,Write,Grep
argument-hint
Hint shown in autocomplete for expected arguments
"[path] [format]"
license
License identifier
MIT
disable-model-invocation
If true, only user-triggered via /skill-name
true
user-invocable
Controls whether skill appears in UI menus
true
context
Execution context; fork runs skill in isolated subagent
fork
agent
Which subagent type when context: fork
code-reviewer
model
Override model when skill is active
sonnet
hooks
Hooks scoped to this skill's lifecycle
See hooks reference
metadata
Arbitrary key-value map for tooling/dashboards
author: your-org
dependencies
Required packages for scripts
python>=3.8, pandas>=1.5.0
bundled-resources
Declared resource files
(list of paths)
distribution
Distribution method
npm, pip, zip
Note: The Skills API uses hyphenated variants (context-fork, model-override). Claude Code uses the names shown above.
Custom Keys (Safe to Use)
Custom keys like category, tags, version are ignored by Claude Code but safe to include for your own tooling (gallery websites, documentation generators, dashboards). They don't conflict with runtime parsing.
Invalid Keys (Confusingly Similar to Valid Ones)
# ❌ These look like valid keys but aren't — use the correct alternativestools:Read,Write# Use 'allowed-tools' insteadintegrates_with: [...] # Use SKILL.md body text insteadoutputs: [...] # Use SKILL.md Output Format section insteadpython_dependencies: [...] # Use 'dependencies' in frontmatter instead
Platform Constraints
Constraint
Limit
Name length
64 characters
Name format
Lowercase letters, numbers, hyphens only
Reserved words in name
"anthropic", "claude" prohibited
Description length
1024 characters
Total skill upload size
8MB (API and claude.ai)
Skills per API request
8 maximum
XML tags in name/description
Prohibited
Cross-surface behavior: Skills do NOT sync across Claude.ai, Claude API, and Claude Code. Each surface requires separate upload/management. Maintain source files in Git as single source of truth.
Recall limits: Too many active skills degrades Claude's selection accuracy. Test coexistence when adding new skills — verify the new skill doesn't steal triggers from existing ones.
Description Formula
Pattern: [What it does] [When to use — be slightly pushy]. NOT for [Exclusions].
The description is the most important line for activation. Claude's runtime scans descriptions to decide which skill to load. A weak description means zero activations or constant false positives.
How activation works: Claude evaluates descriptions semantically, not via keyword matching. It reasons about whether your description covers the user's intent. This means specific, context-rich descriptions outperform keyword lists. Claude also tends to undertrigger — it errs toward NOT activating skills. Combat this by making descriptions slightly pushy: explain when the skill should be used, even if it seems obvious.
Problem
Bad
Good
Too vague
"Helps with images"
"CLIP semantic search for image-text matching and zero-shot classification. NOT for counting, spatial reasoning, or generation."
No exclusions
"Reviews code changes"
"Reviews TypeScript/React diffs and PRs for correctness. NOT for writing new features."
Mini-manual
"Researches, then outlines, then drafts..."
"Structured research producing 1-3 page synthesis reports. NOT for quick factual questions."
Catch-all
"Helps with product management"
"Writes and refines product requirement documents (PRDs). NOT for strategy decks."
Full guide with more examples: See references/description-guide.md
SKILL.md Template
---
name: your-skill-name
description: [What it does] [When to use — be slightly pushy]. NOT for [Exclusions].
allowed-tools: Read,Write
---# Skill Name
[One sentence purpose]
## When to Use
✅ Use for: [A, B, C with specific trigger keywords]
❌ NOT for: [D, E, F — explicit boundaries]
## Core Process
[Mermaid diagrams — 23 types available. See visual-artifacts.md for full catalog]
## Anti-Patterns### [Pattern Name]**Novice**: [Wrong assumption]
**Expert**: [Why it's wrong + correct approach]
**Timeline**: [When this changed, if temporal]
## References-`references/guide.md` — Consult when [specific situation]
-`references/examples.md` — Consult for [worked examples of X]
Collect 3-5 real queries that should trigger this skill, and 3-5 that should NOT.
Step 2: Plan Reusable Contents
For each example, identify what scripts, references, or assets would prevent re-work. Also identify shibboleths: domain algorithms, temporal knowledge, framework evolution, common pitfalls.
After real-world use: notice struggles, improve SKILL.md and resources, update CHANGELOG.md.
Designing Skills for Subagent Consumption
When skills will be loaded by subagents (not just direct user invocation), apply these patterns:
Three Skill-Loading Layers
Preloaded (2-5 core skills): Injected into the subagent's system context. These are its standard operating procedures — always present.
Dynamically selected: Subagent receives a catalog (name + 1-line description) and picks 1-3 matching skills before starting. The orchestrator can also pre-filter.
Execution-time: Subagent reads each skill's "When to use" section, follows numbered steps in order, respects output contracts, and runs QA checks.
How Subagents Should Use Skills
Teach the subagent to treat each skill like a mini-protocol:
Check the "When to use / When not to use" section for applicability
Follow numbered steps in order (adapt only if task constraints force it)
Respect the skill's output contract (templates, JSON shapes, required sections)
Apply QA/validation steps last
Reference skill steps by number: "Completed step 3 of refactor-plan-skill"
Subagent Prompt Structure
The subagent's prompt should have four sections:
Identity: "You are the [role]. You handle [narrow domain]. If outside scope, say so."
Skill usage rules: "Your skills define your methods. Decide which apply, follow their workflows."
Constraints: Quality bar, safety rules, tie-breaking priorities.
Full templates and orchestration patterns: See references/subagent-design.md
Visual Artifacts: Mermaid Diagrams & Code
Skills that include Mermaid diagrams serve two audiences at once. For humans, diagrams render as visual flowcharts, state machines, and timelines — instantly parseable. For agents, Mermaid is a text-based graph DSL — A -->|Yes| B is an explicit, unambiguous edge that's actually easier to reason about than equivalent prose. The agent reads the text; the human sees the picture. Both win.
Rule: If a skill describes a process, decision tree, architecture, state machine, timeline, or data relationship, include a Mermaid diagram. Use raw ```mermaid blocks directly in SKILL.md — not wrapped in outer markdown fences.
All 23 Mermaid Diagram Types
Mermaid supports 23 diagram types. Use the most specific one for your content — a state diagram for lifecycles is better than a flowchart with "go back" arrows.
Skill Content
Diagram Type
Syntax
Decision trees / troubleshooting
Flowchart
flowchart TD
API/agent communication protocols
Sequence
sequenceDiagram
Lifecycle / status transitions
State
stateDiagram-v2
Data models / schemas
ER
erDiagram
Type hierarchies / interfaces
Class
classDiagram
Temporal knowledge / evolution
Timeline
timeline
Domain taxonomy / concept maps
Mindmap
mindmap
Priority matrices (2-axis)
Quadrant
quadrantChart
Component layout / blocks
Block
block-beta
Infrastructure / cloud topology
Architecture
architecture-beta
Multi-level system views (C4)
C4
C4Context / C4Container / C4Component
Project phases / rollout plans
Gantt
gantt
Git branching / release strategy
Git Graph
gitGraph
User experience flows
Journey
journey
Quantity flows / budgets
Sankey
sankey-beta
Metrics / benchmarks
XY Chart
xychart-beta
Proportional breakdowns
Pie
pie
Hierarchical size comparison
Treemap
treemap
Multi-axis capability comparison
Radar
radar
Task/status tracking
Kanban
kanban
Requirements traceability
Requirement
requirementDiagram
Network protocols / binary formats
Packet
packet-beta
Sequence diagrams (code syntax)
ZenUML
zenuml (plugin)
YAML Frontmatter in Mermaid (Optional)
Mermaid supports an optional --- frontmatter block for rendering customization (themes, colors, spacing). It is not required. Agents ignore it. Renderers apply sensible defaults without it. Only add it when you need specific visual styling for published documentation.
# Optional — only for render customization---title:MyDiagramconfig:theme:neutralflowchart:curve:basis---
Full diagram catalog with examples of all 16+ types: See references/visual-artifacts.md
Encoding Shibboleths
Expert knowledge that separates novices from experts. Things LLMs get wrong due to outdated training data or cargo-culted patterns.
Shibboleth Template
### Anti-Pattern: [Name]**Novice**: "[Wrong assumption]"
**Expert**: [Why it's wrong, with evidence]
**Timeline**: [Date]: [Old way] → [Date]: [New way]
**LLM mistake**: [Why LLMs suggest the old pattern]
**Detection**: [How to spot this in code/config]
What to Encode
Framework evolution (React Classes → Hooks → Server Components)
Model limitations (CLIP can't count; embedding models are task-specific)
Tool architecture (Script → MCP graduation path)
API versioning (ada-002 → text-embedding-3-large)
Temporal traps (advice that was correct in 2023 but harmful in 2025)
Full catalog with case studies: See references/antipatterns.md
Self-Contained Tools and the Extension Taxonomy
Skills are one of seven Claude extension types: Skills (domain knowledge), Plugins (packaged bundles for distribution), MCP Servers (external APIs + auth), Scripts (local operations), Slash Commands (user-triggered skills), Hooks (lifecycle automation at 17+ event points), and Agent SDK (programmatic Claude Code access). Most skills should include scripts. MCPs are only for auth/state boundaries. Plugins are for sharing skills across teams/community.
Need
Extension Type
Key Requirement
Domain expertise / process
Skill (SKILL.md)
Decision trees, anti-patterns, output contracts
Packaging & distribution
Plugin (plugin.json)
Bundles skills + hooks + MCP + agents
External API + auth
MCP Server
Working server + setup README
Repeatable local operation
Script
Actually runs (not a template), minimal deps
Multi-step orchestration
Subagent
4-section prompt, skills, workflow
User-triggered action
Slash Command
Skill with user-invocable: true
Lifecycle automation
Hook
17+ events: PreToolUse, PostToolUse, Stop, etc.
Programmatic access
Agent SDK
npm/pip package, CI/CD pipelines
Evolution path: Skill → Skill + Scripts → Skill + MCP Server → Skill + Subagent → Plugin (for distribution). Only promote when complexity justifies it.
Full taxonomy with examples and common mistakes: See references/claude-extension-taxonomy.mdDetailed tool patterns: See references/self-contained-tools.mdPlugin creation and distribution: See references/plugin-architecture.md
Tool Permissions (Least Privilege)
Access Level
allowed-tools
Read-only
Read,Grep,Glob
File modifier
Read,Write,Edit
Build integration
Read,Write,Bash(npm:*,git:*)
⚠️ Never for untrusted
Unrestricted Bash
Anti-Pattern Summary
#
Anti-Pattern
Fix
1
Documentation Dump
Decision trees in SKILL.md, depth in /references
2
Missing NOT clause
Always include "NOT for X, Y, Z" in description
3
Phantom Tools
Only reference files that exist and work
4
Template Soup
Ship working code or nothing
5
Overly Permissive Tools
Least privilege: specific tool list, scoped Bash
6
Stale Temporal Knowledge
Date all advice, update quarterly
7
Catch-All Skill
Split by expertise type, not domain
8
Vague Description
Use [What] [When to use]. NOT for [Exclusions]
9
Eager Loading
Never "read all files first"; lazy-load references
10
Prose-Only Processes
Use Mermaid diagrams (23 types) — flowcharts, sequences, states, ER, timelines, etc.
Full case studies: See references/antipatterns.md
Validation Checklist
□ SKILL.md exists and is <500 lines
□ Frontmatter has name + description (minimum required)
□ Description follows [What][When to use] NOT [Exclusions] formula
□ Description is specific and context-rich (semantic activation, not keyword lists)
□ Name and description are aligned (not contradictory)
□ At least 1 anti-pattern with shibboleth template
□ All referenced files actually exist (no phantoms)
□ Scripts work (not templates), have clear CLI, handle errors
□ Reference files each have a 1-line purpose in SKILL.md
□ Processes/decisions/lifecycles use Mermaid diagrams (23 types), not prose
□ CHANGELOG.md tracks version history
□ If subagent-consumed: output contracts are defined
Run automated checks: python scripts/validate_skill.py <path> and python scripts/validate_mermaid.py <path>
Common Rejection Causes
Cause
Symptom
Fix
Missing name or description
Skill won't load
Add both to frontmatter
tools: instead of allowed-tools:
Tools silently ignored
Use allowed-tools: (hyphenated)
YAML list in allowed-tools
Parse error
Use comma-separated: Read,Write,Edit
Brackets in allowed-tools
Parse error
No [] — just Read,Write,Edit
Invalid keys (triggers, outputs)
Silently ignored or error
Move to SKILL.md body text
Name with spaces/uppercase
May fail matching
Lowercase-hyphenated: my-skill-name
Name doesn't match directory
Activation mismatch
Keep name = directory name
context: not fork
Ignored
Only valid value is fork
disable-model-invocation: not boolean
Ignored
Use true or false
Phantom file references
Agent wastes tool calls
Delete references or create files
Full validation: python scripts/validate_skill.py <path> catches all of these.
Success Metrics
Metric
Target
Correct activation
>90%
False positive rate
<5%
Token usage
<5k tokens
Time to productive
<5 min
Reference Files
Consult these for deep dives — they are NOT loaded by default:
File
Consult When
references/knowledge-engineering.md
KE methods for extracting expert knowledge into skills; protocol analysis, repertory grids, aha! moments
references/description-guide.md
Writing or rewriting a skill description
references/antipatterns.md
Looking for shibboleths, case studies, or temporal patterns
references/self-contained-tools.md
Adding scripts, MCP servers, or subagents to a skill
references/subagent-design.md
Designing skills for subagent consumption or orchestration
references/claude-extension-taxonomy.md
Skills vs Plugins vs MCPs vs Hooks vs Agent SDK — the 7-type taxonomy
references/plugin-architecture.md
Creating, packaging, and distributing plugins via marketplaces
references/visual-artifacts.md
Adding Mermaid diagrams: all 23 types, YAML config, best practices
references/mcp-template.md
Building an MCP server for a skill
references/subagent-template.md
Defining subagent prompts and multi-agent pipelines
