Sends a signed synthetic event to the endpoint's URL and returns the outcome synchronously: whether your endpoint accepted it, the HTTP status it returned, and the round-trip latency. Use it to verify your receiver is reachable and its signature verification is correct. An unreachable endpoint is reported in the response body as `status: failed`, not as a request error. Your endpoint has 10 seconds to respond. The test body is a minimal JSON stub carrying only the event `type` (it does not mirror a real event payload), signed exactly like a real delivery. Test sends go straight to your endpoint: they work on a paused endpoint and are not recorded in [List delivery attempts](/docs/api/reference/list-webhook-attempts). A `412` means the endpoint cannot be tested yet: it has no valid signing secret, or no subscribed event types to fall back on when `event_type` is omitted. Event type to simulate. Any type from the event catalog is accepted, whether or not the endpoint subscribes to it; an unknown type returns a `422`. When omitted, the endpoint's first subscribed event type is used. Whether your endpoint accepted the test event. `delivered` means it returned a `2xx` status; `failed` means it returned a non-`2xx` status or could not be reached (see `error` for the latter). Possible values: `delivered`, `failed` HTTP status returned by your endpoint. Null when no response was received (timeout, connection error, DNS failure). Response body returned by your endpoint, truncated to the first 1024 bytes. Omitted when your endpoint returned no body or could not be reached. Round-trip delivery latency in milliseconds. The full event body delivered to your endpoint. Test sends use a minimal synthetic body rather than a full event payload, so this field is omitted. Event type. Possible values: `whatsapp.sent` Time Bird handed the message to Meta for delivery. Payload of the whatsapp.sent event. ID of the WhatsApp message. ID of the workspace. Whether the message was sent by the business (`outbound`) or received from the contact (`inbound`). Possible values: `outbound`, `inbound` Sender of the message. On outbound messages, the business number it was sent from. Phone number in E.164 format, when known. Business-scoped user ID, Meta's identifier for the WhatsApp user. Present only on the WhatsApp-user side of the message. Recipient of the message. On outbound messages, the WhatsApp contact. Phone number in E.164 format, when known. Business-scoped user ID, Meta's identifier for the WhatsApp user. Present only on the WhatsApp-user side of the message. Tags provided on the send request, echoed on every event for the message. Null when the message carried no tags. The metadata object provided on the send request, echoed on every event for the message. Null when the message carried no metadata. A short explanation of why the event could not be delivered. Present only when your endpoint could not be reached.