> For the complete documentation index, see [llms.txt](https://doc1.antgst.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc1.antgst.com/ant-api/sms/otp-sms.md).

# OTP SMS

**Dear Client,**

To ensure **full integrity** and **data consistency** in your OTP verification workflow, we strongly recommend integrating the **OTP Backfill Interface** alongside your API implementation. Below is the optimized integration logic:

1️⃣ [**Send OTP**](/ant-api/sms/otp-sms/send-otp-sms.md): Invoke the API to deliver SMS verification codes to end users.\
2️⃣ [**OTP Callback**](/ant-api/sms/otp-sms/otp-sms-callback.md): Our system will automatically send delivery reports (DR) to your server once users submit verification codes.\
3️⃣ [**Critical Enhancement – OTP Backfill**](/ant-api/sms/otp-sms/otp-backfill-interface.md):\
 ▸ If the SMS provider fails to return final delivery statuses (e.g., due to network delays or asynchronous responses), this interface allows you to **proactively submit confirmed delivery outcomes**.\
 ▸ Recommended scenarios for triggering backfill:\
  - No callback received within **X minutes** of sending an OTP\
  - User explicitly reports not receiving the SMS\
  - Internal monitoring detects delivery failures

**Benefits of a three-interface integration:**\
✅ **100% status coverage**: Eliminate blind spots in SMS delivery tracking\
✅ **Data accuracy**: Prevent statistical discrepancies caused by missing DRs\
✅ **Seamless UX**: Enable silent retries without user intervention

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