Use when starting a textbook project and the author wants to plan and scaffold the working directory before writing — 规划单本教材项目目录或多教材工作区，可选 git 版本管理与 README 工作说明 — e.g. "初始化教材项目"、"创建教材工作目录"、"规划教材工作区"、"建一个写教材的目录". Only creates the directory scaffold and hands off to textbook; never creates pipeline files (.progress.json、00-教材设计.md、术语表.md). Not for writing textbook content (use textbook — 不经 init 它也会自建默认目录), not for resuming an existing project (directly use textbook).
Use when writing one textbook chapter following the fixed 四段式 structure (概念讲解 → 示范例题 → 引导练习 → 独立习题) from an outline slice plus UbD anchor — e.g. "写第三章"、"按大纲写这一章". Usually orchestrated by textbook; can run standalone for a deep-dive technical article with worked examples. Not for designing outlines or whole-book orchestration.
Use when generating verified STEM exercises with Bloom-level tags — 示范例题（完整解题过程）、引导练习（带提示）、独立习题（附参考答案）— e.g. "出几道矩阵乘法的练习题"、"给这一章生成例题". Every computational answer is actually verified (真算核对) before output. Usually called by textbook-chapter; can run standalone. Not for 文科论述题 (v2) or exam paper assembly.
Use when a textbook project needs its teaching design — 教学定位、UbD 预期结果五件套（大概念/持久理解/核心问题/迁移目标/学习目标）、章节树与例题 Bloom 梯度规划 — e.g. "设计教材大纲"、"教材规划"、"课程体系设计". Usually orchestrated by textbook; can run standalone to produce 00-教材设计.md. Not for writing chapter prose or generating exercises.
Use when the user wants to write a complete multi-chapter textbook or systematic course material with exercises — e.g. "写教材"、"写一本教材"、"编写课程讲义"、"系统教材"、"textbook". Orchestrates a five-stage UbD-driven pipeline (教学定位 → UbD 预期结果 gate → 章节树 gate → 逐章写作 → 审核定稿) with resumable progress via .progress.json. Not for single tutorials (use tutorial-writer), single chapters (use textbook-chapter), or exercise-only requests (use textbook-exercises).