Sidepanel-based Chrome extension that turns Substack into a usable Contact CRM for readers — and adds a writing assist toolkit (TOC, pre-publish checklist, AI search optimization score, AI-powered SEO suggestions) for posts.

Status: pre-release. Currently being developed by @south0120. Chrome Web Store listing in preparation.

• Take memos directly on Substack profile pages — free-form notes + tags
• "Add to history" — capture comments, URLs, and context with one click
• Bookmarks tab in the sidepanel collects every saved post
• Cross-search by name, tag, or memo content
• Pin / archive / JSON export-import
• Auto-syncs to each profile's brand color

Activates inside the Substack post editor (/publish/post/<id>).

• Auto Table of Contents with proper nested indentation (h2/h3/h4+ as 3 levels)
• Live word count + reading time — updates every 4 seconds while typing
• Pre-publish checklist — body length, headings, image alts, hooks, citations, paragraph length (8 signals)
• AI Search Score — 7-signal heuristic that scores how well the post is structured for retrieval-style AI search (Perplexity, ChatGPT search, Claude). Grade A–D
• AI SEO suggest — generate 3 SEO title and 3 SEO description candidates via Anthropic / OpenAI / Google APIs (BYO key)

• All Contact Memo / Bookmark data is stored in chrome.storage.sync — Chrome's standard sync area. Nothing leaves your browser unless you opt into AI features.
• AI API key (Anthropic / OpenAI / Google) is stored in chrome.storage.local — local-only, never synced across devices.
• The AI SEO suggest feature, only when explicitly invoked, sends the article's title and body to your selected provider. No analytics, no tracking, no third-party.

1. Clone this repo
2. Visit chrome://extensions/ in Chrome
3. Toggle Developer mode (top-right)
4. Click Load unpacked → select the cloned folder
5. Pin the extension and click its icon to open the side panel

manifest.json               # MV3 manifest
background.js               # service worker (just opens side panel on action)
content.js                  # injected on profile pages — Contact Memo widget
toc.js                      # injected on post pages — TOC + stats + body-text RPC
sidepanel.html / .js / .css # main UI (Contact Memo + Writing Assist)
storage.js                  # chrome.storage.sync wrapper with local fallback
i18n.js                     # ja / en strings
icons/                      # 16/48/128 PNG icons
store_publication_kit/      # listing copy, privacy policy, screenshots guide

There is no build step. Edit files in place, then click "Reload" on the extension card in chrome://extensions/.

TBD — to be decided before public release.

@south0120 (newsletter: サウスのAI活動報告書).