markdown-chapter-splitter

markdown-chapter-splitter is a skill for Claude Code, Codex from Tano73/agent-skills. It costs 145 tokens per session (1,457 once invoked), scanned A, original, MIT.

A tool that splits a long Markdown file into separate files, one for each top-level chapter heading. It keeps subsections with their chapter and can preserve introductory material separately.

In plain words
What is it for?
Use it for books, manuals, long notes, or documentation organized with Markdown `#` headings. It creates an ordered sibling folder with safely named chapter files.
Why use it?
It makes large documents easier to navigate, edit, and reuse. It also avoids treating headings inside code examples as real chapter boundaries.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it for books, manuals, long notes, or documentation organized with Markdown # headings. It creates an ordered sibling folder with safely named chapter files.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/tano73/agent-skills/markdown-chapter-splitter
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add Tano73/agent-skills --skill markdown-chapter-splitter
Clone the repo
git clone --depth 1 https://github.com/Tano73/agent-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for markdown-chapter-splitter

README.md
[![agentmods](https://agentmods.dev/badge/skills/tano73/agent-skills/markdown-chapter-splitter.svg)](https://agentmods.dev/skills/tano73/agent-skills/markdown-chapter-splitter)
Your own site
<a href="https://agentmods.dev/skills/tano73/agent-skills/markdown-chapter-splitter"><img src="https://agentmods.dev/badge/skills/tano73/agent-skills/markdown-chapter-splitter.svg" alt="Measured on agentmods" height="20"></a>
Per session 145 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,457 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00145 $0.01457
Opus 5 $0.00072 $0.00728
Sonnet 5 $0.00029 $0.00291
Haiku 4.5 $0.00015 $0.00146

Measured 6d ago against content hash 4af8e997ef97, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

markdown-chapter-splitter scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/split_markdown_by_chapter.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/markdown-chapter-splitter/SKILL.md · 128 lines

How it starts

The opening of the file, as written. The whole thing — 128 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Markdown Chapter Splitter

Use this skill to turn one large Markdown file into a sibling folder of smaller .md files, with one file per top-level chapter.

Default behavior

  • Treat only level-1 headings (# Heading) as chapter boundaries.
  • Keep nested sections (##, ###, and deeper) inside the same chapter file.
  • Write output in a sibling folder named <input-stem>/ (same name as the file without extension) unless the user explicitly asks for a different path.
  • If the source contains content before the first # chapter (frontmatter, title page, preface, introduction), save it as 00-preface.md.
  • Generate chapter filenames from the chapter title, sanitized for filesystem safety and prefixed with chapter order, for example:
    • 01-introduction.md
    • 02-system-design.md
  • Preserve the original chapter heading as the first heading in each chapter file.
  • Ignore # lines inside fenced code blocks so code samples do not create false chapter splits.
  • If no reliable H1 chapters are found, or only one H1 chapter is found, try the bundled text-chapter heuristic before giving up on chapter splitting.
  • The heuristic should recognize common book-style chapter markers such as:
    • CHAPTER 5 followed by a title on the next line
    • Chapter One. Crunching Knowledge
    • Chapter 3. Mapping to Relational Databases
    • ## CHAPTER 1 Layered Architecture
    • ## 1 followed by ## WHAT IS DESIGN AND ARCHITECTURE?
  • The heuristic should prefer real chapter starts over table-of-contents entries.

When to ask before running

Ask the user instead of assuming if:

  • the input file path is missing or ambiguous
  • they want split points based on ## or another heading level
  • they want a custom output directory or naming scheme
  • they want frontmatter copied into every chapter file instead of a separate preface file
  • they explicitly do not want automatic text-based chapter inference

Workflow

  1. Resolve the input .md file path and confirm it exists.
  2. Set the output directory:
    • default: <same-directory>/<input-stem>/ (directory named after the file stem, no -chapters suffix)
    • custom: only if the user explicitly asked for one
  3. Run the bundled splitter script in default mode first:

Read the full file on GitHub · 128 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 128 lines · 145 tokens per session scan A 4af8e997ef97

Subscribe to this mod's changes

markdown-chapter-splitter is a skill published in the GitHub repository Tano73/agent-skills (2 stars, last pushed 3d ago), licensed MIT. It adds 145 tokens to every session and 1,457 once invoked, about $0.0007 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Related

Other skills, from other repositories

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.

obra/superpowers · 21 tokens

local-ai-agents

Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…

microsoft/ai-agents-for-beginners · 200 tokens

next-cache-components-adoption

Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…

vercel/next.js · 95 tokens

next-partial-prefetching-adoption

Turn on Partial Prefetching in a Next.js app and work through the insights it surfaces. Use when the user wants to enable or adopt Partial Prefetching, flip the partialPrefetching flag, opt routes in with export const prefetch = 'partial', audit Link prefetch={true} behavior, preserve existing prefetched UI with…

vercel/next.js · 103 tokens

chronicle

Analyze Copilot session history for standup reports, usage tips, session search, and session reindexing. Use when the user asks for a standup, daily summary, usage tips, workflow recommendations, wants to search or find past sessions by keyword/file/PR, wants to reindex their session store, or asks about deleting…

microsoft/vscode · 72 tokens

babysit-pr

Babysit a GitHub pull request after creation by continuously polling review comments, CI checks/workflow runs, and mergeability state until the PR is merged/closed or user help is required. Diagnose failures, retry likely flaky failures up to 3 times, auto-fix/push branch-related issues when appropriate, and keep…

openai/codex · 114 tokens