# Request

The caller’s request was wrong: unreadable, incomplete, or a value that breaks a rule. 400 or 422.

Pattern: `request.*` (this page) · Raised with: [`fail()`](https://www.prongs.dev/docs/profiles/errors.md) · Intents: [3](#intents) · Statuses: `400` `422`

## Intents

| Intent | Status | Use it for |
|---|---|---|
| [`request.malformed`](https://www.prongs.dev/docs/intents/request/malformed.md) | `400` | The request cannot be read: invalid JSON, the wrong content type |
| [`request.missing`](https://www.prongs.dev/docs/intents/request/missing.md) | `400` | A required field or parameter is absent |
| [`request.invalid`](https://www.prongs.dev/docs/intents/request/invalid.md) | `422` | A field breaks a rule: too long, the wrong format, out of range |

## Raising one

Name what went wrong. The intent sets the status, the message the caller sees, and any log it writes.

```ts
// The request cannot be read: invalid JSON, the wrong content type
return fail('request.malformed', 'Invalid JSON.');

// A required field or parameter is absent
return fail('request.missing', 'Handle is required.');

// A field breaks a rule: too long, the wrong format, out of range
return fail('request.invalid', 'Use 1–32 lowercase letters, numbers, or hyphens.');
```

The caller gets (request.malformed)

```bash
HTTP 400

{
  "ok": false,
  "error": "Invalid JSON.",
  "code": "request.malformed"
}
```

## Is it a request error?

Find the row that describes your case, and use the domain on the right.

| If the problem is | Use |
|---|---|
| The caller’s request was wrong: unreadable, incomplete, or a value that breaks a rule. 400 or 422. | `request.*` (this page) |
| No valid credentials: nobody signed in, an expired session, a bad token or secret. 401. | [`auth.*`](https://www.prongs.dev/docs/intents/auth.md) |
| Valid credentials, but not allowed to do this. 403. | [`permission.*`](https://www.prongs.dev/docs/intents/permission.md) |
| The thing asked for is not there, as far as the caller may know. 404. | [`record.*`](https://www.prongs.dev/docs/intents/record.md) |
| The request clashes with the current state: it already exists, or it is not possible yet. 409. | [`conflict.*`](https://www.prongs.dev/docs/intents/conflict.md) |
| Too many requests, or an allowance used up. 429. | [`limit.*`](https://www.prongs.dev/docs/intents/limit.md) |
| Our fault or a dependency’s. The caller sees a generic message; the details are logged. 5xx. | [`failure.*`](https://www.prongs.dev/docs/intents/failure.md) |

## For registry authors

**Starter intents.** These are the intents `prongs add errors` puts in your registry, raised with [`fail()`](https://www.prongs.dev/docs/profiles/errors.md). Change the messages to suit your app, and the statuses through the [`status.*`](https://www.prongs.dev/docs/intents/errors.md#status) intents they are built from.