Teach your AI how you write

Margin with highlights and margin notes

Most AI writing tools try to fix your words after the fact. Margin works the other way — you mark up what's wrong, and your corrections compound into rules your AI follows before it writes.

Built for annotating

If the tool doesn't feel good to sit in, you won't annotate. If you don't annotate, your AI never learns.

Style Memory

The biggest gap in AI writing isn't capability — it's that your AI doesn't know what you sound like. Style Memory closes that gap. React to what your AI gets wrong, and your preferences compound into a system it actually follows.

Corrections

When your AI writes something wrong — wrong tone, wrong phrasing, wrong instinct — highlight it and add a note. Margin captures the original text, your feedback, and the surrounding context. Tag each correction with a writing type so rules stay scoped.

generalemailprdblogcover-letterresumeslackpitchoutreach

Corrections with voice signals exported to file

# Writing Rules

_For AI agents: apply rules matching the writing type._
_General rules always apply._

## General

### Voice Calibration

**Rule: Almost never end messages with periods
(~0.8%). This is the single strongest voice
signal.** [must-fix]
- When to apply: All casual and semi-formal writing
- Why: Periods on short messages are the #1 AI tell
- Signal: seen 10 time(s)

### Ai Slop

**Rule: Eliminate sentence patterns that signal
AI-generated text.** [must-fix]
- Before: "The deeper issue isn't that AI features
  are hard to build in-house. It's that AI makes it
  trivially easy..."
- After: "AI makes it trivially easy for anyone to
  reverse-engineer product surface area."

### Authenticity

**Rule: Remove any claim you do not genuinely
believe or cannot defend with your own
experience.** [must-fix]
- Why: Readers and interviewers will probe claims;
  inauthentic ones collapse under scrutiny.

# ~/.claude/hooks/margin-writing-guard.sh
# Auto-generated by Margin — regenerated on rules export

KILL_WORDS=("leverage" "utilize" "furthermore"
            "moreover" "additionally")

for word in "${KILL_WORDS[@]}"; do
  if grep -qi "$word" "$1"; then
    echo "BLOCKED: '$word' violates your writing rules"
    exit 1
  fi
done

What you can do with it

Margin's MCP server exposes your documents, annotations, and rules to Claude. These are real workflows, not hypotheticals.

Diff review for AI edits

Claude Code edits your file. Margin notices. An FSEvents watcher detects changes, shows a diff banner, and renders inline diffs with green insertions and red deletions. Review each change and keep or revert it — one hunk at a time.

20+ MCP tools

Your documents, annotations, corrections, and writing rules — exposed to any MCP-compatible AI client. Read files, create highlights, search across your library, export rules as prompt-ready markdown.

// Example: highlight text and attach a note
{
  "tool": "margin_highlight_by_text",
  "arguments": {
    "document_id": "abc-123",
    "text_to_highlight": "We leverage AI to optimize",
    "color": "pink",
    "note": "Kill this. Say 'we use AI to save time.'"
  }
}

Works the way your Mac does