Use when designing a module interface, when it exports nearly as much as it hides or is as complicated as its implementation, or when tiny one-function modules multiply.
Install
npx skills add yutna/functional-design-skills --skill functional-designing-deep-modulesnpx skills add yutna/functional-design-skills --skill functional-designing-deep-modules -a claude-code -gnpx skills add yutna/functional-design-skills --skill functional-designing-deep-modules -a codex -ggemini skills install https://github.com/yutna/functional-design-skills.git --path plugin/skills/functional-designing-deep-modulesgh skill install yutna/functional-design-skills functional-designing-deep-modulesgit clone --depth 1 https://github.com/yutna/functional-design-skills /tmp/yutna__functional-design-skills
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/yutna__functional-design-skills/plugin/skills/functional-designing-deep-modules ~/.claude/skills/functional-designing-deep-modules # Claude Code
cp -R /tmp/yutna__functional-design-skills/plugin/skills/functional-designing-deep-modules ~/.agents/skills/functional-designing-deep-modules # Codex, Cursor, Gemini CLI, Copilot, OpenCode