Add Skill Quality Standards section

Add quality standards reference section with canonical links (AgentSkills.io
spec, Anthropic best practices, anthropics/skills repo) and concise criteria
table covering description style, progressive disclosure, no absolute paths,
and scoped tools.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -63,6 +63,7 @@ The most contributed Agent Skills repository, built and maintained together with
 - [Skills by WordPress Development Team](#skills-by-wordpress-development-team)
 - [Skills by Transloadit Team](#skills-by-transloadit-team)
 - [Community Skills](#community-skills)
+- [Skill Quality Standards](#skill-quality-standards)
 
 
 ### Skills Paths for Other AI Coding Assistants
@@ -638,6 +639,25 @@ Domain-specific knowledge for Azure SDK and Foundry development.
 
 </details>
 
+## Skill Quality Standards
+
+As the ecosystem grows, consistent quality helps agents discover and use skills reliably. The following references and criteria keep the bar high.
+
+### Canonical References
+
+- **[AgentSkills.io Spec](https://agentskills.io)** -- The open standard for skill metadata, structure, and interoperability across tools.
+- **[Anthropic Best Practices](https://platform.claude.com)** -- Official guidance on writing effective skills for Claude Code.
+- **[anthropics/skills](https://github.com/anthropics/skills)** -- Anthropic's official skills repository, useful as a reference implementation.
+
+### Quality Criteria
+
+| Area | Guideline |
+|------|-----------|
+| **Description** | Write in third person. State *what* the skill does and *when* to use it. Use specific keywords agents can match on (e.g., "PostgreSQL migration" not "database stuff"). |
+| **Progressive disclosure** | Keep top-level metadata under ~100 tokens. Skill body should stay below 500 lines. Load resources (large docs, schemas) on demand, not inline. |
+| **No absolute paths** | Never hard-code machine-specific paths like `/Users/alice/`. Use relative paths or well-known variables (`$HOME`, `$PROJECT_ROOT`). |
+| **Scoped tools** | Request only the tools the skill actually needs. Avoid blanket `"tools": ["*"]`. Declare tool dependencies explicitly. |
+
 ## 🤝 Contributing
 
 We welcome contributions! See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.