Classification

A closed label set beats free text every time: the set lowers to a JSON Schema enum, the provider’s structured output enforces it, and the runtime re-validates the answer — a wrong label triggers a correction retry that lists the allowed values. The label set is the TypeScript type you already have.

Three native forms

src/classify.tsi

export type Category = "billing" | "refund" | "fraud" | "other";

export enum Sentiment {
  Positive = "positive",
  Neutral = "neutral",
  Negative = "negative",
}

export infer function classifyMessage(.message: string) {
  const category = ask ..`the category of the customer message`<Category>;
  const sentiment = ask ..`the overall sentiment of the message`<Sentiment>;
  const urgent = ask ..`does the message need urgent attention`<"yes" | "no">;
  return { category, sentiment, urgent: urgent === "yes" };
}

• A string-literal union alias (Category) — the lightest form; the result is typed as the union.
• A string enum (Sentiment) — also a runtime value, so consumers compare with Sentiment.Negative.
• An inline union (<"yes" | "no">) — handy for a one-off, mapped to a boolean in plain TypeScript right there.

No separate schema DSL and no generated mirror types; the three asks share .message because context belongs to the invocation.

Consuming the result

src/main.ts

import { classifyMessage, Sentiment } from "./classify.tsi";

const result = await classifyMessage("I was charged twice for order #4711 and nobody answers the phone.");

if (result.category === "fraud" || (result.sentiment === Sentiment.Negative && result.urgent)) {
  console.log("escalate", result);
} else {
  console.log("queue", result);
}

Once an ask returns, its value is an ordinary typed value — branch on it, pass it around, put it in an object.

Confidence and rationale

Ask for them as further typed values in the same invocation:

src/classify-confident.tsi

export type Category = "billing" | "refund" | "fraud" | "other";

export infer function classifyWithConfidence(.message: string) {
  const category = ask ..`the category of the customer message`<Category>;
  const confidence = ask ..`how confident is the "${category}" classification, from 0 to 1`<number>;
  const rationale = ask ..`one sentence explaining why the message is "${category}"`<string>;
  return { category, confidence, rationale };
}

Asks in one invocation share the contextual parameters, but not each other’s answers — the second and third asks see category only because it is interpolated with ${}. See The ask operator.

What is not there yet

Per-label descriptions — a hint attached to each variant of the union or enum — have no Nola equivalent at 0.1.x (a planned follow-up). Until then, put the guidance in a JSDoc comment on the alias or in the instruction text.

Next: Function calling