# Show calculator help to users [#show-calculator-help-to-users]

Use this guide when your UI needs labels, required facts or validation help
for the selected calculator.

## Before you start [#before-you-start]

* Choose a calculator ID such as `au.pay.take-home`.
* Use HTTP for browser clients that cannot import rule packages.
* Keep the generated OpenAPI reference as the endpoint field source.

## Steps [#steps]

1. Fetch calculator schema metadata.
2. Render fact titles and question metadata.
3. Call calculate with `help=errors` when validation fails.
4. Show returned issue paths beside your fields.

## Example [#example]

```ts
import { TaxKitHttpApiService } from "@taxkit/api-http/client";
import { createTaxKitApiClientLayer } from "@taxkit/api-http/client/live";
import { HelpQuery } from "@taxkit/calculators/schemas";
import { AuPayTakeHomeCalculation } from "@taxkit/sdk/au/effect";
import { Array, Effect, Layer, Option } from "effect";
import * as FetchHttpClient from "effect/http/FetchHttpClient";

export const loadCalculatorHelp = Effect.gen(function* () {
  const client = yield* TaxKitHttpApiService;
  const query = yield* HelpQuery.makeEffect({
    help: Option.some(Option.some("schema")),
  });
  const schema = yield* client.calculatorApi.getCalculatorSchema({
    params: { calculatorId: AuPayTakeHomeCalculation.calculatorId },
    query,
  });
  return Array.map(schema.inputFacts, (fact) => `${fact.id}: ${fact.title}`);
});

// Your application supplies the public API origin and owns Effect execution.
export const program = loadCalculatorHelp.pipe(
  Effect.provide(
    createTaxKitApiClientLayer({ baseUrl: "http://127.0.0.1:4000" }).pipe(
      Layer.provide(FetchHttpClient.layer)
    )
  )
);
```

## Verify the result [#verify-the-result]

Expected output includes fact descriptors for gross pay and the tax-free
threshold claim used by the take-home pay calculator.

## Handle errors [#handle-errors]

Let the typed client's expected error channel reach your application error
handler. Display the checked issue paths or descriptor help from an input
decode failure; [API errors](/api/errors) explains the envelope and other
server failures. A calculation call with `help=errors` returns field help when
its checked request facts do not match the selected calculator.

## Related pages [#related-pages]

* [Facts](/concepts/facts)
* [Diagnostics](/concepts/diagnostics)
* [API errors](/api/errors)