SMSTAKE Voice API

Overview

SMSTAKE Voice is an HTTPS JSON API at https://api.smstake.com/v1/voice/. Use it for outbound dialer (OBD) broadcasts, text-to-speech calls, voice OTP as a fallback when SMS is not enough, and IVR menus that collect keypad input. Place calls only to numbers that your use case is allowed to reach. Prompts, routes and the languages enabled on an account are confirmed during onboarding.

Related guides: Voice (OBD/IVR), SMS API, RCS API, and the SMSTAKE blog.

Authentication

Send one of these headers on every call to https://api.smstake.com/v1/voice/. Do not send both.

Authorization: Bearer YOUR_API_TOKEN
Content-Type: application/json

X-API-Key: YOUR_API_KEY
Content-Type: application/json

• Use HTTPS only.
• Store the token or API key in an environment variable. Do not commit it to source control.
• Rotate it from the SMSTAKE account, or contact support if it is exposed.

Outbound voice call

Endpoint: POST https://api.smstake.com/v1/voice/call. This places an automated outbound call. Play a file already stored on the account, or speak a script with text-to-speech. Send audio_file_id or text_to_speech, not both.

Text-to-speech examples

curl -X POST "https://api.smstake.com/v1/voice/call" \
  -H "Authorization: Bearer $SMSTAKE_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "phone": "+919876543210",
    "text_to_speech": "Your order is out for delivery today.",
    "language": "en",
    "callback_url": "https://yourapp.com/webhooks/smstake/voice",
    "client_ref": "tts_order_1001"
  }'

import os, requests
resp = requests.post(
    "https://api.smstake.com/v1/voice/call",
    headers={"Authorization": f"Bearer {os.environ['SMSTAKE_API_TOKEN']}"},
    json={
        "phone": "+919876543210",
        "text_to_speech": "Your order is out for delivery today.",
        "language": "en",
        "callback_url": "https://yourapp.com/webhooks/smstake/voice",
        "client_ref": "tts_order_1001",
    },
    timeout=30,
)
print(resp.json())

const res = await fetch("https://api.smstake.com/v1/voice/call", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SMSTAKE_API_TOKEN}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    phone: "+919876543210",
    text_to_speech: "Your order is out for delivery today.",
    language: "en",
    callback_url: "https://yourapp.com/webhooks/smstake/voice",
    client_ref: "tts_order_1001"
  })
});
console.log(await res.json());

Recorded audio

Use audio_file_id when the prompt is already uploaded. The same clients work with an API key header instead of Bearer.

{
  "phone": "+919876543210",
  "audio_file_id": "audio_festive_01",
  "callback_url": "https://yourapp.com/webhooks/smstake/voice",
  "client_ref": "obd_festive_01"
}

curl -X POST "https://api.smstake.com/v1/voice/call" \
  -H "X-API-Key: $SMSTAKE_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @call.json

Success response

Store call_id so you can match later status and DTMF webhooks.

{
  "status": "accepted",
  "call_id": "call_8f3k2j9x1m",
  "phone": "+919876543210",
  "client_ref": "tts_order_1001"
}

Voice OTP

Endpoint: POST https://api.smstake.com/v1/voice/otp. Use this when you need a spoken verification call, for example as a fallback after SMS OTP. Put the code in text_to_speech, with spaces between digits so it is read clearly. The same fields as an outbound call apply.

curl -X POST "https://api.smstake.com/v1/voice/otp" \
  -H "Authorization: Bearer $SMSTAKE_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "phone": "+919876543210",
    "text_to_speech": "Your verification code is 4 8 2 9 1 3.",
    "language": "en",
    "callback_url": "https://yourapp.com/webhooks/smstake/voice",
    "client_ref": "otp_login_1001"
  }'

import os, requests
code = " ".join("482913")
resp = requests.post(
    "https://api.smstake.com/v1/voice/otp",
    headers={"X-API-Key": os.environ["SMSTAKE_API_KEY"]},
    json={
        "phone": "+919876543210",
        "text_to_speech": f"Your verification code is {code}.",
        "language": "hi",
        "callback_url": "https://yourapp.com/webhooks/smstake/voice",
        "client_ref": "otp_login_1001",
    },
    timeout=30,
)
print(resp.json())

const code = "482913".split("").join(" ");
const res = await fetch("https://api.smstake.com/v1/voice/otp", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.SMSTAKE_API_KEY,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    phone: "+919876543210",
    text_to_speech: `Your verification code is ${code}.`,
    language: "hi",
    callback_url: "https://yourapp.com/webhooks/smstake/voice",
    client_ref: "otp_login_1001"
  })
});
console.log(await res.json());

A successful OTP call returns the same shape as an outbound call, with its own call_id.

Languages

Set language when you send text_to_speech. English and Hindi are the usual starting points. Other regional Indian languages use the same field when that language is enabled on your account.

Call status and DTMF

Register an HTTPS URL on the SMSTAKE account, or send callback_url on the request. SMSTAKE posts JSON as the call moves. Return 200 OK as soon as the event is stored. When signing is enabled, verify X-SMSTAKE-Signature against the raw body. Deduplicate on call_id plus event. For call.dtmf, also include digits, because one call can send more than one key press.

call.answered

POST https://yourapp.com/webhooks/smstake/voice
Content-Type: application/json
X-SMSTAKE-Signature: sha256=<hex-encoded HMAC-SHA256 of the raw body>

{
  "event": "call.answered",
  "call_id": "call_8f3k2j9x1m",
  "phone": "+919876543210",
  "status": "answered",
  "client_ref": "tts_order_1001",
  "occurred_at": "2026-10-21T14:15:08+05:30"
}

call.dtmf

Use digits to drive an IVR step, such as confirming an appointment when the recipient presses 1.

{
  "event": "call.dtmf",
  "call_id": "call_8f3k2j9x1m",
  "phone": "+919876543210",
  "digits": "1",
  "client_ref": "tts_order_1001",
  "occurred_at": "2026-10-21T14:15:20+05:30"
}

call.initiated and call.completed

{ "event": "call.initiated", "call_id": "call_8f3k2j9x1m", "phone": "+919876543210", "status": "initiated", "client_ref": "tts_order_1001", "occurred_at": "2026-10-21T14:15:02+05:30" }

{ "event": "call.completed", "call_id": "call_8f3k2j9x1m", "phone": "+919876543210", "status": "completed", "client_ref": "tts_order_1001", "occurred_at": "2026-10-21T14:15:41+05:30" }

HTTP status

Related docs

• Developer portal
• SDKs and Postman
• Voice (OBD/IVR) service
• SMSTAKE SMS API
• SMSTAKE RCS API
• SMSTAKE WhatsApp API
• OTP SMS guide
• SMSTAKE blog
• Request API access