Build EPUB 3.3 from raw chapter files. Pure Python (lxml + zipfile), no external EPUB libs. Accepts .xhtml, .html, .md, .txt. Filename prefix order (001_, 002_...) = reading order.
Markdown + YAML → validated EPUB 3.3. Auto EPUBCheck: 0 fatal / 0 error / 0 warning. EPUB 3.3 + OCF 3.3 + Accessibility 1.1 + legacy NCX for Kindle and Kobo.
Package any writing style as an AI-readable skill. Output: simple .md or full .skill package. Four sections: Voice & Tone, Sentence Mechanics, Paragraph Patterns, What to Avoid.