How book-to-skill Structures the Generated Agent Skill: A Complete Directory Layout Guide

The book-to-skill converter creates a self-contained Agent Skill with a strict directory layout anchored by SKILL.md, three supporting reference files, and templated chapter summaries organized under a chapters/ subdirectory.

The book-to-skill project transforms source books into importable Agent Skills that AI assistants can consume directly. According to the virgiliojr94/book-to-skill source code, the converter enforces a predictable, hierarchical structure designed for machine readability, token-budget compliance, and host-agnostic portability.

Top-Level Skill Folder Structure

When the conversion workflow reaches Step 6 — Create skill directory structure — it creates a root directory under the host-specific skill home ($SKILLS_HOME/<skill_name>)【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L33-L38】.

The resulting layout always follows this pattern:

<skill_root>/
│   SKILL.md                # Master descriptor (≤ 4,000 tokens)

│   glossary.md             # Alphabetized term definitions

│   patterns.md             # Concrete techniques and design patterns

│   cheatsheet.md           # Decision tables and quick-reference rules

└── chapters/
        ch01-<slug>.md      # Chapter 1 summary

        ch02-<slug>.md      # Chapter 2 summary

        …

This structure separates discovery content (root-level index files) from deep content (chapter summaries), letting agents load only what they need.

SKILL.md: The Master Descriptor

The root SKILL.md serves as the skill's entry point and must stay within 4,000 tokens (Step 9)【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L57-L70】【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L94-L100】.

Its required sections include:

• Front-matter — skill name, version, source book metadata
• Usage Guide — how to invoke the skill in an agent context
• Core Frameworks & Mental Models — condensed knowledge graph
• Chapter Index — navigable table linking to each chapters/*.md file
• Topic Index — cross-reference by concept rather than chapter sequence
• Supporting Files — links to glossary.md, patterns.md, cheatsheet.md

The Chapter Index uses a standard markdown table format:

| # | Title | Key Frameworks |

|---|-------|----------------|
| [ch01](chapters/ch01-intro.md) | Introduction | Framework A, Principle B |
| [ch02](chapters/ch02-deep-dive.md) | Deep Dive | Technique X |

Chapter Files and the Templating System

Each chapter file in chapters/ follows a strict template defined in Step 7【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L63-L84】. A fully populated chapter (ch03-design-patterns.md) contains these sections:

# Chapter 3: Design Patterns

## Core Idea

One sentence that captures the chapter's main takeaway.

## Frameworks Introduced

- **Factory Method**: when you need to instantiate objects without specifying concrete classes.
  - When to use: configuration-heavy systems, plugin architectures
  - How: define Creator interface with factory_method() returning Product

## Key Concepts

- **Abstraction** — hiding implementation details (Ch 3)

## Mental Models

- Think of a factory as a *recipe* that produces objects.

## Anti-patterns

- **God Object** — a class that knows too much; leads to tight coupling.

## Code Examples

```python
class Product:
    pass

class ConcreteProductA(Product):
    pass

class Creator:
    def factory_method(self) -> Product:
        return ConcreteProductA()

Worked Example

A step-by-step walkthrough of applying Factory Method to build a plugin system.

Key Takeaways

1. Prefer composition over inheritance for extensibility
2. Keep product hierarchies shallow
3. Document the contract, not the implementation

Connects To

• Ch 2: Object fundamentals
• Design Thinking: Problem framing techniques

The template adapts based on **book type** and **depth setting**:

| Book Type | Sections Omitted | Sections Added |
|-----------|------------------|----------------|
| Text-only (no code) | `Code Examples`, `Reference Tables` | — |
| Technical (with code) | — | `Code Examples` |
| `DEPTH=reference` | `Worked Example` | — |
| `DEPTH=study` | — | `Worked Example`【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L94-L106】 |

## Supporting Reference Files

Three specialized files complete the **Agent Skill structure**, each with strict token budgets:

### glossary.md

Alphabetized list of terms formatted as `**Term** — definition (Ch N)`. Limited to **~1,500 tokens** (Step 8)【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L26-L30】.

Example entry:

```markdown
**Dependency Inversion** — depend on abstractions, not concretions; enables testability and swapping implementations (Ch 5)

patterns.md

Catalog of techniques, algorithms, and design patterns. Each entry includes When to use and How subsections. Budget: ≤ 2,000 tokens【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L32-L36】.

cheatsheet.md

Compact decision support: flowcharts, trade-off matrices, thresholds, rules of thumb. Budget: ~1,200 tokens【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L38-L48】.

All three files are referenced from SKILL.md in its Supporting Files section【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L110-L115】.

Validation and Security Scanning

Before completion, Step 9.5 runs tools/scan_generated_skill.py to enforce safety constraints【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L28-L32】:

• No prompt-injection patterns in markdown content
• No unsafe authority claims or executable directives
• File sizes within token budgets
• Required sections present in all chapter files

Run the scanner manually:

python -m tools.scan_generated_skill ~/.copilot/skills/my-skill-slug

The scanner's implementation lives at /tools/scan_generated_skill.py in the repository.

Practical Usage Examples

Convert a book to a structured skill

# Full conversion workflow (Steps 0-9)

book-to-skill path/to/book.pdf my-skill-slug

Inspect generated structure

tree ~/.copilot/skills/my-skill-slug

Load in GitHub Copilot CLI

copilot ask "apply the core frameworks from my-skill-slug to my project"

Implementation Files

File	Purpose
SKILL.md	Blueprint defining directory layout, token limits, and template specifications【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md】
tools/scan_generated_skill.py	Security and compliance scanner【/cache/repos/github.com/virgiliojr94/book-to-skill/master/tools/scan_generated_skill.py】
book_to_skill/utils.py	create_skill_structure() and render_chapter_template() implementations
tools/validate_skill.py	Host-specific validator (Claude, Copilot, Amp lenses)【/cache/repos/github.com/virgiliojr94/book-to-skill/master/tools/validate_skill.py】

Summary

• book-to-skill generates self-contained directory structures with four root files plus a chapters/ subdirectory
• SKILL.md acts as the master index with a 4,000-token hard limit and standardized navigation tables
• Chapter files follow a rigid template with contextually omitted sections based on book type and depth setting
• Three supporting files (glossary.md, patterns.md, cheatsheet.md) provide quick-reference material within strict token budgets
• scan_generated_skill.py validates security and structural compliance before the skill is considered complete

Frequently Asked Questions

What determines the folder name for a generated skill?

The skill name is decided in Step 5 of the workflow and becomes the directory name under $SKILLS_HOME/. The converter slugifies the provided name to ensure filesystem-safe paths【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L33-L38】.

Can I manually edit files after generation?

Yes, but re-running the scanner is recommended. The tools/scan_generated_skill.py script checks for token budget violations and unsafe content patterns that manual edits might introduce【/cache/repos/github.com/virgiliojr94/book-to-skill/master/tools/scan_generated_skill.py】.

How does the skill handle books without code examples?

For text-only books, the template omits the Code Examples and Reference Tables sections automatically. The Frameworks Introduced and Mental Models sections carry the knowledge transfer instead【/cache/repos/github.com/virgiliojr94/book-to-skill/master/SKILL.md#L94-L106】.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}