Skill Builder
Purpose
Creates production-ready Agent Skills following the official specifications and best practices.
When I Activate
I automatically load when you mention:
- "build a skill" or "create a skill"
- "generate a skill" or "make a skill"
- "design a skill" or "new skill"
Authoritative References (Read These First)
Before creating any skill, read the current versions of these docs:
- Agent Skills Specification (the open standard): https://agentskills.io/specification
- Skill Authoring Best Practices (Anthropic): https://platform.claude.com/docs/en/agents-and-tools/agent-skills/best-practices
- Claude Code Skills Documentation (Claude Code extensions): https://docs.claude.com/en/docs/claude-code/skills
- Example Skills (reference implementations): https://github.com/anthropics/skills
These are the source of truth. If anything in this skill contradicts those docs, the official docs win.
What I Do
Create skills in 5 steps:
- Clarify → Define purpose, scope, activation keywords
- Design → Plan structure, decide on progressive disclosure
- Generate → Create SKILL.md with proper frontmatter and body
- Validate → Check against spec and best practices
- Test → Verify activation and behavior
Frontmatter (Agent Skills Spec)
Only two fields are required:
---
name: my-skill
description: What this skill does and when to use it. Include specific keywords for discovery.
---Optional fields: license, compatibility, metadata, allowed-tools.
Claude Code adds: disable-model-invocation, user-invocable, model, context, agent, hooks, argument-hint.
Do NOT use: version (use metadata.version), auto_activates, priority_score, source_urls, evaluation_criteria, invokes, philosophy, maturity — none of these are recognized by any runtime.
Key Best Practices
From the official best practices:
Conciseness
- Claude is already smart. Only add context it doesn't have.
- Challenge every paragraph: "Does this justify its token cost?"
- SKILL.md body under 500 lines.
Description Quality
- Write in third person ("Processes Excel files", not "I help you")
- Include both what the skill does AND when to use it
- Include specific trigger keywords for discovery
- Max 1024 characters
Progressive Disclosure
- Metadata loaded at startup (name + description only)
- SKILL.md loaded when skill activates
- Supporting files loaded only when needed
- Keep references one level deep from SKILL.md
Degrees of Freedom
- High freedom: Multiple valid approaches, context-dependent
- Medium freedom: Preferred pattern exists, some variation OK
- Low freedom: Fragile operations, exact sequence required
No Time-Sensitive Content
- Never write "as of today", "recently added", "new in v3.0"
- Use an "old patterns" section for historical context if needed
Feedback Loops
- Run validator → fix errors → repeat
- Include verification steps for critical operations
Validation Checklist
✅ Frontmatter: name and description present and valid ✅ Name: Lowercase, hyphens only, 1-64 chars, matches directory name ✅ Description: 1-1024 chars, third person, includes trigger keywords ✅ Body: Under 500 lines ✅ References: One level deep from SKILL.md ✅ No stale content: No temporal references ✅ Consistent terminology: One term per concept throughout ✅ Tested: Works with at least 3 representative prompts
Supporting Files
- reference.md: Detailed patterns, architecture, validation rules
- examples.md: Skill creation workflows and examples