Fallback API

The Fallback API is part of the OmniChannel Send API. It lets you send messages with fallback across primary channels — SMS, RCS, and WhatsApp — in a single API call. If the primary channel fails to deliver within the configured wait time, the platform retries on the fallback channel(s) you define.

Endpoint

POST https://api.onexaura.com/oapi/send_sms

The Fallback API uses the same endpoint as the OmniChannel send API. Fallback behavior is activated by including the fallback object in the request body.

Headers

string

required

API key issued by OneXtel, used for authentication.

Request body

The request body is a JSON object. Each top-level key represents a messaging channel. You may use any one of sms, wa, or rcs as your primary channel, plus a fallback object defining the fallback behavior.

`sms` — SMS channel (array of objects)

string

required

SMS sender ID.

string

required

Recipient phone number.

string

required

Message type. Verified accepted on the SMS send API: SI, OTP, SE. Case-sensitive.

Neither TXN nor TRANS is a valid message type, despite both having appeared in earlier example payloads. Live testing of the SMS send API (Aug 2026) accepts only SI, OTP, and SE; TXN, TRANS, and Promo are rejected as invalid type.This matters more in fallback than in a direct send: an invalid type here is rejected at the fallback stage, long after the primary send returned 200, so the symptom is a successful API response and no SMS. Use SI or SE for service messages — see DLT template types.

The accepted set was verified on the send API, not on the fallback object specifically. If a fallback SMS is still not arriving with a valid type, confirm the fallback validator uses the same set.

string

required

Message content.

string

DLT template ID. Optional only when template auto-match is enabled on the API key; otherwise required for DLT-registered SMS in India.

string

DLT entity ID. Optional only when template auto-match is enabled on the API key; otherwise required for DLT-registered SMS in India.

With template auto-match enabled on the API key, OneXtel matches messageBody against your registered DLT templates and fills in templateId and entityId. When you do pass both, they are used as sent.

number

0 or 1 — enable Unicode encoding. Optional.

object

Optional custom reference fields for tracking or tagging (e.g. CustomReference1, CustomReference2).

`wa` — WhatsApp channel (array of objects)

string

required

Always "whatsapp".

string

required

Always "individual".

array

required

Array of recipient phone numbers.

string

required

WhatsApp sender number. A Pool ID can also be passed.

string

required

Always "template".

object

required

Object with name, language.code (the template language), and components. Uses the same payload structure as the WhatsApp Template Message API.

string

Custom reference fields for tracking: custref1 through custref5. Optional.

`rcs` — RCS channel (array of objects)

string

required

RCS sender ID.

string

required

Message type.

string

required

Recipient phone number.

object

required

Contains templateMessage, an object with templateCode and customParams. Uses the same payload structure as the RCS Template Message API.

string

Custom reference fields for tracking: custref1 through custref5. Optional.

`fallback` — fallback configuration (object)

Defines fallback behavior when the primary channel fails to deliver.

string

required

Fallback configuration ID.

boolean

required

Set to true to enable fallback.

string

required

Maximum time (in seconds) to wait for Delivery / Failure before triggering fallback. If the primary message carries a ttl longer than this wait time, the wait time overrides the TTL, so the primary attempt ends when fallback fires and the recipient does not get both messages.

object

SMS fallback object: sender, type, messageBody plus optional unicode, templateId, entityId, and custRef1–custRef5. Include as per your fallback configuration. templateId and entityId follow the same auto-match rule as the sms channel above.

object

WhatsApp fallback object: sender, template, languageCode, templateComponents (same payload structure as the WhatsApp Template Message API) plus optional custref1–custref5. Include as per your fallback configuration.

object

RCS fallback object: sender, messageType, templateCode, customParams (same payload structure as the RCS Template Message API) plus optional custref1–custref5. Include as per your fallback configuration.

Fallback Channel 1 and Fallback Channel 2 details can be added as per your fallback configuration. If a third-party fallback is used, dynamic keys can be added with the specific channel name.

Optional top-level fields

string

Phone number prefix, e.g. "+91". Optional.

string

Campaign identifier string. Optional.

object

Object with flag (set to 1 — mandatory if a URL shortener is required in the message body) and a urlDetails array. Each urlDetails item contains longUrl (mandatory when flag is 1), domain (optional), and track_user (optional).

Example request

The example below sends a WhatsApp template message as the primary channel with SMS configured as the fallback channel.

curl --request POST \
  --url https://api.onexaura.com/oapi/send_sms \
  --header 'apikey: YOUR_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
  "wa": [
    {
      "messaging_product": "whatsapp",
      "recipient_type": "individual",
      "recipient": [
        "919999999999",
        "919999999998"
      ],
      "sender": "YOUR_WA_SENDER",
      "type": "template",
      "template": {
        "name": "YOUR_TEMPLATE_NAME",
        "language": {
          "code": "en"
        },
        "components": []
      }
    }
  ],
  "fallback": {
    "fallback_id": "YOUR_FALLBACK_ID",
    "fallback": true,
    "waittime": "30",
    "sms": {
      "sender": "YOUR_SMS_SENDER",
      "type": "SI",
      "messageBody": "Your message text",
      "templateId": "YOUR_DLT_TEMPLATE_ID",
      "entityId": "YOUR_DLT_ENTITY_ID"
    }
  }
}'

{
  "sms": [
    {
      "sender": "YOUR_SMS_SENDER",
      "recipient": "919999999999",
      "type": "SI",
      "messageBody": "Your message text",
      "templateId": "YOUR_DLT_TEMPLATE_ID",
      "entityId": "YOUR_DLT_ENTITY_ID",
      "unicode": 0,
      "custRef1": {
        "CustomReference1": "",
        "CustomReference2": ""
      }
    }
  ],
  "wa": [
    {
      "messaging_product": "whatsapp",
      "recipient_type": "individual",
      "recipient": [
        "919999999999",
        "919999999998"
      ],
      "sender": "YOUR_WA_SENDER",
      "type": "template",
      "template": {
        "name": "YOUR_TEMPLATE_NAME",
        "language": {
          "code": "en"
        },
        "components": []
      }
    }
  ],
  "rcs": [
    {
      "sender": "YOUR_RCS_SENDER",
      "messageType": "template",
      "recipient": "919999999999",
      "contentMessage": {
        "templateMessage": {
          "templateCode": "YOUR_TEMPLATE_CODE",
          "customParams": "{}"
        }
      },
      "custref1": "",
      "custref2": "",
      "custref3": "",
      "custref4": "",
      "custref5": ""
    }
  ],
  "fallback": {
    "fallback_id": "YOUR_FALLBACK_ID",
    "fallback": true,
    "waittime": "30",
    "sms": {
      "sender": "YOUR_SMS_SENDER",
      "type": "SI",
      "messageBody": "Your message text",
      "unicode": 0,
      "templateId": "YOUR_DLT_TEMPLATE_ID",
      "entityId": "YOUR_DLT_ENTITY_ID"
    },
    "wa": {
      "sender": "YOUR_WA_SENDER",
      "template": "YOUR_TEMPLATE_NAME",
      "languageCode": "en",
      "templateComponents": []
    },
    "rcs": {
      "sender": "YOUR_RCS_SENDER",
      "messageType": "template",
      "templateCode": "YOUR_TEMPLATE_CODE",
      "customParams": "{}"
    }
  }
}

Include only the channel array (sms, wa, or rcs) that you want as the primary channel, and only the fallback channel objects that match your fallback configuration. The example under “Request body (all channels)” shows every supported block in one payload for reference.

WhatsApp

RCS

SMS (India)

SMS (International)

OmniChannel

Verify

Endpoint

Headers

Request body

`sms` — SMS channel (array of objects)

`wa` — WhatsApp channel (array of objects)

`rcs` — RCS channel (array of objects)

`fallback` — fallback configuration (object)

Optional top-level fields

Example request

​Endpoint

​Headers

​Request body

​sms — SMS channel (array of objects)

​wa — WhatsApp channel (array of objects)

​rcs — RCS channel (array of objects)

​fallback — fallback configuration (object)

​Optional top-level fields

​Example request

Endpoint

Headers

Request body

`sms` — SMS channel (array of objects)

`wa` — WhatsApp channel (array of objects)

`rcs` — RCS channel (array of objects)

`fallback` — fallback configuration (object)

Optional top-level fields

Example request