undertone

Hear how it sounds before you hit send. A text box that reads the tone of your message as you type and grows into a reading of it: it glows in the tone's color, tells you if it's boss-safe, and points at the exact phrases doing the damage.

Per my last email, I need the deck ASAP.    →  Passive-aggressive · Not boss-safe
So sorry to bother you, no worries if not!  →  Over-apologizing
Can't wait for Friday, you're all amazing!  →  Reads excited
k.                                          →  Reads cold

How it works

One TypeSafe AI Jev call answers eight typed questions about the message in parallel: overall tone, passive-aggression, sarcasm, over-apologizing, pushiness, urgency, formality, and whether you'd send it to your manager. Plain code turns those answers into a verdict, a color and phrase-level tips.

Without an API key it falls back to a built-in keyword classifier, so it runs out of the box.

Run it

Requires Bun.

bun install
bun dev

To use the online model:

cp .env.example .env.local   # then set TYPESAFE_API_KEY

The key is read only on the server, in /api/tone.

Layout

src/
  app/api/tone/route.ts   POST { text } → ToneResult
  lib/jev/                Jev questions and server client
  lib/tone/               reading model, offline classifier, verdict, phrase tips
  hooks/use-tone.ts       debounced, abortable fetch
  components/tone/        composer card, verdict badge, meters, tips

Scripts

Command	What it does
bun dev	Start the dev server
bun run check	Typecheck, lint and test
bun run build	Production build