What problem does it solve? Creating Claude Code extensions requires knowing many scattered rules: SKILL.md frontmatter formats, sub-agent tool lists, plugin manifests, hook events, settings hierarchy, and sandboxing options. This Skill consolidates the official authoring guidance into one reference so extensions are built correctly the first time. ## Core Features & Use Cases - Skill Authoring: Progressive disclosure structure, frontmatter rules, and the 500-line SKILL.md limit with validation checklists. - Extension Coverage: Reference docs for sub-agents, plugins, slash commands, hooks, memory, settings, sandboxing, headless mode, dev containers, and CLI usage. - Agent Patterns: Orchestrator-worker architectures, two-agent long-task patterns, context engineering, and tool design best practices. - Use Case: When adding a new project Skill or configuring a PreToolUse hook in settings.json, consult this kit to get the exact frontmatter fields, file locations, and common pitfalls (rationalizations, red flags, verification steps). ## Quick Start Ask Claude to create a new Claude Code Skill or configure a hook using the moai-foundation-cc authoring guidance.