# Preview a voice-call template

`POST https://evohub.io/api/v1/voice-template/preview`

Part of the [On-Call API](https://docs-dev.evohub.io/oncall.md) reference · operationId `previewVoiceTemplate`.

Renders a template without saving it: `spoken` is the whole call script,
`rendered` the template's own part (cut at 200 characters, `truncated`). The
fields are filled from sample values the organization's alerts have carried.
It also reports names no alert has ever sent (`unknown_fields`, likely typos),
which integrations send each name, the integrations whose alerts carry every
name (`complete_on`), and names that were empty in this sample.

**Permission (API-key scope):** `oncall:settings:write`.

## Authorization

Any one of:

- `bearerAuth` (oncall:settings:write)
- `apiKeyHeader` (oncall:settings:write)

Where:

- `bearerAuth`: HTTP Bearer — An EvoHub API key (`evohub_…`) as a bearer token.
- `apiKeyHeader`: API key in the header `X-API-Key` — An EvoHub API key (`evohub_…`).

## Request body (required)

Content type: `application/json`

Type: `VoiceTemplateWrite`

- `body` (string, max length 1000): Placeholders in braces, e.g. `{alert.title}` or `{service}`.

## Responses

### 200 — The preview.

Content type: `application/json`

Type: `object`

- `data` (VoicePreview, required)
  - `spoken` (string)
  - `rendered` (string)
  - `truncated` (boolean)
  - `alert_title` (string)
  - `unknown_fields` (array of string)
  - `field_sources` (object)
    - Other keys: array of string
  - `complete_on` (array of string)
  - `blank_fields` (array of string)
- `success` (boolean, required, value `true`)

### 400 — The body is not valid JSON (`INVALID_BODY`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required): Machine-readable code. Branch on this.
  - `message` (string, required): Human-readable explanation.

### 401 — No API key was sent, or it is unknown, revoked or expired (`UNAUTHORIZED`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required): Machine-readable code. Branch on this.
  - `message` (string, required): Human-readable explanation.

### 403 — The key lacks the scope this endpoint needs (`FORBIDDEN`).

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required): Machine-readable code. Branch on this.
  - `message` (string, required): Human-readable explanation.

### 429 — Too many requests (`RATE_LIMITED`). Wait `Retry-After` seconds.

Headers:

- `Retry-After` (integer): Seconds to wait.

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required): Machine-readable code. Branch on this.
  - `message` (string, required): Human-readable explanation.

### 500 — Something went wrong on EvoHub's side (`INTERNAL_ERROR`). Retry later.

Content type: `application/json`

Type: `Error`

- `error` (object, required)
  - `code` (string, required): Machine-readable code. Branch on this.
  - `message` (string, required): Human-readable explanation.

## Example request

```bash
curl -X POST 'https://evohub.io/api/v1/voice-template/preview' \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer <TOKEN>' \
  -d '{
  "body": "Service {service} in {env}: {alert.title}."
}'
```