is-odd-jev

Check whether a number is odd, using a System One model, with a calibrated probability.

npm i is-odd-jev

const isOdd = require('is-odd-jev');

await isOdd(5);
// { odd: true, p: 0.999, ms: 71, output_tokens: 3 }

await isOdd(4);
// { odd: false, p: 0.002, ms: 88, output_tokens: 3 }

npx is-odd-jev 5

Why

is-odd (2014) returns a boolean. It cannot tell you how sure it is.

is-odd-ai (2023) asks an LLM, which returns a string you then parse, and which will happily invent a confidence score if you ask it for one.

is-odd-jev returns p — the model's actual probability that n is odd, computed from the distribution rather than narrated. Jev's Noul primitive has no confidence field, because the probability is the answer. If you need a symmetric certainty:

const { odd, p } = await isOdd(n);
const confidence = Math.abs(p - 0.5) * 2;

Which lets you do the thing you could never do with an LLM:

if (confidence >= 0.95) ship(odd);
else escalateToHuman(n);

Pick that threshold by measuring it on a held-out set, not by intuition.

Setup

Node 18+. Zero dependencies.

| env | default | |---|---| | TYPESAFE_API_KEY | — | | AI_GATEWAY_API_KEY | — (fallback, see below) | | TYPESAFE_BASE_URL | https://api.typesafe.ai | | TYPESAFE_DEFAULT_MODEL | jev-latest |

Without a TypeSafe key

Direct TypeSafe keys are waitlisted. Vercel AI Gateway serves the same model as typesafe-ai/jev with no waitlist, so this works instead:

export AI_GATEWAY_API_KEY=...
npx is-odd-jev 5

TYPESAFE_API_KEY wins if both are set. Two things genuinely differ through the gateway:

• Probabilities come back rounded, usually to 2dp — you get 0.99, not 0.999.
• The free tier is rate-limited hard on this model. Fine for one number, not for a loop.

Under the hood the gateway calls a Noul a boolean and its answer probability, and takes the model in a header rather than the body. This package handles that; if you are calling it yourself, experimental_evaluate from ai@7 speaks it natively:

import { experimental_evaluate as evaluate } from 'ai';

const { answers } = await evaluate({
  model: 'typesafe-ai/jev',
  state: { n: 5 },
  questions: { odd: { type: 'boolean', instructions: 'Is n odd?' } },
});

What it sends

{
  "model": "jev-latest",
  "state": { "n": 5 },
  "questions": { "odd": { "type": "noul", "instructions": "Is n odd?" } }
}

It cannot chat. It cannot explain itself. It cannot hallucinate. It can only tell you, with a calibrated probability, that five is odd.

Prior art

• is-odd — depends on is-number. is-even depends on is-odd.
• is-odd-ai — asks GPT, parses the reply.
• n % 2 === 1 — still correct, still 0 ms, still free.

MIT