Skill Design Guide

Skill Design Guide

Interactive guide for building Claude skills from scratch. Walks users through the full lifecycle: use case definition, folder structure, frontmatter, instructions, design patterns, testing, iteration, and distribution.

What Is a Skill

A skill is a folder containing instructions that teach Claude how to handle specific tasks or workflows. Instead of re-explaining preferences and processes every conversation, skills teach Claude once.

Required file: SKILL.md — main instructions in Markdown with YAML frontmatter.

Optional directories:

• scripts/ — executable code (Python, Bash, etc.)
• references/ — documentation loaded as needed
• assets/ — templates, fonts, icons used in output

Progressive disclosure (three levels):

1. YAML frontmatter — always loaded in system prompt. Tells Claude when to use the skill.
2. SKILL.md body — loaded when Claude thinks the skill is relevant. Full instructions.
3. Linked files — scripts, references, assets. Loaded only as needed.

Three skill categories:

1. Document and Asset Creation — consistent output (docs, presentations, code, designs)
2. Workflow Automation — multi-step processes with consistent methodology
3. MCP Enhancement — workflow guidance on top of MCP tool access

Instructions

Guide the user through each step interactively. Ask clarifying questions before moving to the next step. Do not rush — quality of each step matters more than speed through the workflow.

Step 1: Define Use Cases

Ask the user for 2-3 concrete use cases the skill should enable.

For each use case, capture:

• Trigger: What the user would say (e.g., "help me plan this sprint")
• Steps: What the workflow involves
• Tools: Built-in Claude capabilities, MCP tools, or scripts needed
• Result: What success looks like

Example of a well-defined use case:

Use Case: Project Sprint Planning
Trigger: User says "help me plan this sprint" or "create sprint tasks"
Steps:
1. Fetch current project status from Linear (via MCP)
2. Analyze team capacity
3. Suggest task prioritization
4. Create tasks in Linear with proper labels and estimates
Result: Fully planned sprint with tasks created

Determine whether the skill is standalone or MCP-enhanced. Standalone skills use Claude's built-in capabilities only. MCP-enhanced skills coordinate with one or more MCP servers.

Step 2: Set Up Folder Structure

Create the skill folder following these rules:

Folder naming (kebab-case only):

• notion-project-setup — correct
• Notion Project Setup — wrong (spaces, capitals)
• notion_project_setup — wrong (underscores)
• NotionProjectSetup — wrong (capitals)

Inside the folder:

• SKILL.md — required, exact casing (not SKILL.MD, skill.md, etc.)
• scripts/ — if executable code is needed
• references/ — if detailed documentation is needed
• assets/ — if templates or static files are needed
• No README.md inside the skill folder (docs go in SKILL.md or references/)

Step 3: Write YAML Frontmatter

The frontmatter is how Claude decides whether to load the skill. This is the most important part to get right.

Required format:

---
name: your-skill-name
description: What it does. Use when user asks to [specific phrases].
---

Required fields:

• name — kebab-case, no spaces or capitals, should match folder name
• description — must include WHAT the skill does AND WHEN to use it, under 1024 characters, no XML angle brackets

Optional fields:

• license — e.g., MIT, Apache-2.0
• compatibility — environment requirements (1-500 chars)
• metadata — custom key-value pairs (author, version, mcp-server, etc.)

Security restrictions:

• No XML angle brackets in frontmatter
• No "claude" or "anthropic" in the skill name (reserved)

Consult references/yaml-frontmatter-reference.md for the complete field reference.

Step 4: Write the Description Field

The description determines whether the skill triggers correctly. Structure it as:

[What it does] + [When to use it] + [Key capabilities]

Good descriptions:

# Specific and actionable
description: Analyzes Figma design files and generates developer handoff
  documentation. Use when user uploads .fig files, asks for "design specs",
  "component documentation", or "design-to-code handoff".

# Includes trigger phrases
description: Manages Linear project workflows including sprint planning,
  task creation, and status tracking. Use when user mentions "sprint",
  "Linear tasks", "project planning", or asks to "create tickets".

# Clear value proposition
description: End-to-end customer onboarding workflow for PayFlow. Handles
  account creation, payment setup, and subscription management. Use when
  user says "onboard new customer", "set up subscription", or "create
  PayFlow account".

Bad descriptions:

# Too vague — won't trigger reliably
description: Helps with projects.

# Missing triggers — Claude won't know when to load it
description: Creates sophisticated multi-page documentation systems.

# Too technical, no user triggers
description: Implements the Project entity model with hierarchical relationships.

If there is risk of over-triggering, add negative triggers:

description: Advanced data analysis for CSV files. Use for statistical
  modeling, regression, clustering. Do NOT use for simple data exploration
  (use data-viz skill instead).

Step 5: Write Main Instructions

After the frontmatter, write the instructions in Markdown. Follow this structure:

# Your Skill Name

## Instructions

### Step 1: [First Major Step]

Clear explanation of what happens.

Example:
python scripts/fetch_data.py --project-id PROJECT_ID
Expected output: [describe what success looks like]

(More steps as needed)

## Examples

### Example 1: [Common scenario]

User says: "Set up a new marketing campaign"
Actions:

1. Fetch existing campaigns via MCP
2. Create new campaign with provided parameters
   Result: Campaign created with confirmation link

## Troubleshooting

### Error: [Common error message]

Cause: [Why it happens]
Solution: [How to fix]

Best practices:

• Be specific and actionable — show exact commands, expected outputs
• Include error handling for common failures
• Reference bundled files clearly: "Consult references/api-patterns.md for rate limiting guidance"
• Use numbered lists and bullet points over prose
• Put critical instructions at the top with clear headers
• Keep SKILL.md under 5,000 words — move detailed docs to references/

For critical validations, consider bundling a script that performs checks programmatically rather than relying on language instructions. Code is deterministic; language interpretation is not.

Step 6: Choose a Design Pattern

Help the user select the pattern that fits their use case:

1. Sequential Workflow Orchestration — multi-step processes in a specific order with dependencies between steps
2. Multi-MCP Coordination — workflows spanning multiple services (e.g., Figma to Drive to Linear to Slack)
3. Iterative Refinement — output quality improves with validation and iteration loops
4. Context-Aware Tool Selection — same outcome, different tools depending on context (file type, size, etc.)
5. Domain-Specific Intelligence — specialized knowledge beyond tool access (compliance, regulations, best practices)

Consult references/design-patterns.md for detailed examples and key techniques for each pattern.

Step 7: Test the Skill

Guide the user through three testing areas:

Triggering tests:

• Does it load on obvious task requests?
• Does it load on paraphrased requests?
• Does it stay silent on unrelated topics?

Test queries that should trigger:

"Help me set up a new [Service] workspace"
"I need to create a project in [Service]"
"Initialize a [Service] project for Q4 planning"

Test queries that should NOT trigger:

"What's the weather?"
"Help me write Python code"
"Create a spreadsheet" (unless the skill handles sheets)

Functional tests:

• Valid outputs generated
• API/MCP calls succeed
• Error handling works
• Edge cases covered

Performance comparison: Compare with and without the skill on the same task. Track: number of messages, failed API calls, tokens consumed, and whether user corrections were needed.

Debugging tip: Ask Claude "When would you use the [skill-name] skill?" Claude will quote the description back — adjust based on what's missing.

Step 8: Iterate

Skills are living documents. Watch for these signals:

Under-triggering (skill doesn't load when it should):

• Add more trigger phrases and keywords to the description
• Include technical terms users might use
• Check if the description is too narrow

Over-triggering (skill loads for unrelated queries):

• Add negative triggers ("Do NOT use for...")
• Narrow the scope of the description
• Clarify specific file types or services

Execution issues (skill loads but results are inconsistent):

• Improve instruction specificity
• Add error handling
• Use scripts for deterministic checks instead of language instructions
• Put critical instructions at the top and repeat key points

Pro tip: Iterate on a single challenging task until Claude succeeds, then extract the winning approach into the skill. This provides faster signal than broad testing.

Step 9: Distribute

Claude.ai upload:

1. Zip the skill folder
2. Settings then Capabilities then Skills then Upload
3. Toggle the skill on

Claude Code: Place the skill folder in the Claude Code skills directory.

Organization-level deployment: Admins can deploy skills workspace-wide with automatic updates and centralized management.

GitHub (recommended for sharing):

• Public repo with clear README (repo-level, separate from skill folder)
• Example usage and screenshots
• Link from MCP documentation if applicable

API (programmatic use):

• /v1/skills endpoint for listing and managing skills
• container.skills parameter in Messages API
• Works with Claude Agent SDK for custom agents

When writing about the skill, focus on outcomes not features:

Good: "Set up complete project workspaces in seconds instead of 30 minutes
of manual setup."

Bad: "A folder containing YAML frontmatter and Markdown instructions that
calls our MCP server tools."

References

For detailed information beyond these instructions:

• references/yaml-frontmatter-reference.md — complete field reference with types, constraints, and annotated examples
• references/design-patterns.md — all 5 design patterns with full example structures and key techniques
• references/troubleshooting.md — common issues from upload errors to triggering problems to MCP failures
• references/quality-checklist.md — pre-upload and post-upload validation checklist
• references/source/ — full original guide chapters (00 through 06) for authoritative deep reference