# Cast SMS API — Developer Documentation

**Base URL:** `https://api.cast.ph`
**API Version:** v1

---

## Overview

The Cast API allows you to send SMS, OTP, and SIM messages programmatically. All API requests must be authenticated using an API key provided by Cast.

---

## Authentication

All requests to the SMS and OTP endpoints require an API key passed in the request header.

**Header:**
```
X-API-Key: cast_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
```

API keys have the format `cast_` followed by 64 hexadecimal characters. Keep your API key secret — do not expose it in client-side code or public repositories.

---

## Endpoints

### 1. Send SMS

**`POST /api/sms/send`**

Sends an SMS message to the specified destination number.

#### Request Headers

| Header | Required | Value |
|--------|----------|-------|
| `X-API-Key` | Yes | Your API key |
| `Content-Type` | Yes | `application/json` |

#### Request Body

```json
{
  "to": "09171234567",
  "message": "Hello, this is a test message.",
  "sender_id": "CAST"
}
```

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `to` | string | Yes | Recipient phone number. Must be an 11-digit Philippine mobile number (e.g. `09171234567`). |
| `message` | string | Yes | Message content. Max 300 characters (2 SMS parts). Absolute limit is 450 characters (3 SMS parts). |
| `sender_id` | string | No | Sender ID to use. Max 11 characters. Must be pre-approved. Defaults to your assigned sender ID if only one is configured. |

#### Success Response — `200 OK`

```json
{
  "success": true,
  "message_id": "abc123def456",
  "parts": 1
}
```

| Field | Type | Description |
|-------|------|-------------|
| `success` | bool | `true` if the message was sent. |
| `message_id` | string | Gateway-assigned message identifier. |
| `parts` | int | Number of SMS parts (standard SMS = 1 part per 160 characters). |

---

### 2. Send Bulk SMS

**`POST /api/sms/bulk`**

Sends the same SMS message to multiple recipients in a single API call. Up to **1,000 destinations** per request.

Credits are checked upfront for the full batch before any messages are sent. Each destination is sent individually and logged separately, so partial success is possible if a send fails mid-batch.

#### Request Headers

| Header | Required | Value |
|--------|----------|-------|
| `X-API-Key` | Yes | Your API key |
| `Content-Type` | Yes | `application/json` |

#### Request Body

```json
{
  "to": ["09171234567", "09181234567", "09191234567"],
  "message": "Hello, this is a broadcast message.",
  "sender_id": "CAST"
}
```

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `to` | array of strings | Yes | List of recipient phone numbers. Min 1, max 1,000. Each must be a valid phone number. |
| `message` | string | Yes | Message content to send to all recipients. |
| `sender_id` | string | No | Sender ID to use. Must be pre-approved. Defaults to your assigned sender ID if only one is configured. |

#### Success Response — `200 OK`

```json
{
  "success": true,
  "total": 3,
  "sent": 3,
  "failed": 0,
  "results": [
    { "to": "09171234567", "success": true, "message_id": "abc123", "parts": 1 },
    { "to": "09181234567", "success": true, "message_id": "def456", "parts": 1 },
    { "to": "09191234567", "success": true, "message_id": "ghi789", "parts": 1 }
  ]
}
```

| Field | Type | Description |
|-------|------|-------------|
| `success` | bool | `true` only if all destinations were sent successfully. |
| `total` | int | Total number of destinations in the request. |
| `sent` | int | Number of messages successfully sent. |
| `failed` | int | Number of messages that failed. |
| `results` | array | Per-destination result. Each entry includes `to`, `success`, and on success: `message_id` and `parts`. On failure: `error`. |

**Note:** The HTTP status is always `200` when the request itself is valid, even if some individual sends failed. Check `success` and `failed` in the response body to detect partial failures.

#### Error Response (request-level) — `402`, `400`, `403`

Request-level errors (invalid input, insufficient credits, bad sender ID) return a flat error response — no `results` array:

```json
{
  "success": false,
  "error": "insufficient credits: need 6, have 3"
}
```

---

### 3. Send OTP

**`POST /api/otp/send`**

Sends an OTP (One-Time Password) message. Identical to the SMS endpoint but routed through a dedicated OTP gateway.

#### Request Headers

Same as [Send SMS](#1-send-sms).

#### Request Body

Same as [Send SMS](#1-send-sms).

#### Success Response

Same as [Send SMS](#1-send-sms).

---

### 4. Send SIM

**`POST /api/sim/send`**

Sends a message via a SIM gateway (SMPP-to-SIM). Same request and response shape as Send SMS, but routed through the SIM pool.

> **Account requirement:** The `sim` channel must be explicitly enabled on your account. Accounts default to SMS and OTP only. Contact Cast to enable SIM access.

#### Request Headers

Same as [Send SMS](#1-send-sms).

#### Request Body

Same as [Send SMS](#1-send-sms).

#### Success Response

Same as [Send SMS](#1-send-sms).

#### Additional Error Responses

| Status | Error | Cause |
|--------|-------|-------|
| `403 Forbidden` | `"sim channel not enabled for this account"` | Your account does not have SIM access |
| `503 Service Unavailable` | `"sim service is disabled"` | The SIM gateway is not configured on the platform |

---

### 5. Send Bulk SIM

**`POST /api/sim/bulk`**

Sends the same message to multiple recipients via the SIM gateway. Identical to [Send Bulk SMS](#2-send-bulk-sms) in behavior and response shape, but routed through the SIM pool.

> **Account requirement:** Same as [Send SIM](#4-send-sim) — the `sim` channel must be enabled on your account.

#### Request Headers

Same as [Send SMS](#1-send-sms).

#### Request Body

Same as [Send Bulk SMS](#2-send-bulk-sms).

#### Success Response

Same as [Send Bulk SMS](#2-send-bulk-sms).

#### Additional Error Responses

| Status | Error | Cause |
|--------|-------|-------|
| `403 Forbidden` | `"sim channel not enabled for this account"` | Your account does not have SIM access |
| `503 Service Unavailable` | `"sim service is disabled"` | The SIM gateway is not configured on the platform |

---

## Error Handling

All errors return a JSON body in this format:

```json
{
  "success": false,
  "error": "error message here"
}
```

### HTTP Status Codes

| Status Code | Meaning |
|-------------|---------|
| `200 OK` | Request succeeded |
| `400 Bad Request` | Invalid or missing request fields |
| `401 Unauthorized` | Missing or invalid API key |
| `402 Payment Required` | Insufficient credits |
| `403 Forbidden` | Access denied (see below) |
| `429 Too Many Requests` | Rate limit exceeded |
| `500 Internal Server Error` | Unexpected server error |
| `503 Service Unavailable` | SMS/SIM service is temporarily disabled |

### Common Error Messages

| Error Message | Status | Cause |
|---------------|--------|-------|
| `"missing X-API-Key header"` | 401 | No API key provided |
| `"invalid api key"` | 401 | API key not found or invalid |
| `"api key is revoked"` | 403 | API key has been deactivated |
| `"api key has expired"` | 403 | API key passed its expiration date |
| `"user account is inactive"` | 403 | Account has been disabled |
| `"ip not whitelisted"` | 403 | Request origin IP is not in the allowed list |
| `"sim channel not enabled for this account"` | 403 | SIM access is not enabled on your account |
| `"insufficient credits: need X, have Y"` | 402 | Not enough credits to send the message |
| `"no sender IDs assigned to this user"` | 403 | No sender ID has been configured for your account |
| `"sender_id 'X' is not allowed for this user"` | 403 | The specified sender ID is not approved for your account |
| `"to is required"` | 400 | The `to` field is missing |
| `"to must be 7-15 characters"` | 400 | Phone number is not a valid length |
| `"message is required"` | 400 | The `message` field is missing |
| `"message is too long (max 450 characters)"` | 400 | Message exceeds the 3-part SMS limit |
| `"sender ID is too long (max 11 characters)"` | 400 | Sender ID exceeds the character limit |

---

## Rate Limits

| Limit | Value |
|-------|-------|
| Requests per second | 30 |
| Burst (max simultaneous) | 50 |

When you exceed the rate limit, the API returns `429 Too Many Requests` with a `Retry-After: 60` header. Wait the specified number of seconds before retrying.

---

## SMS Parts & Credits

SMS messages are divided into **parts** based on length:

| Encoding | Single SMS | Multi-part SMS (per part) |
|----------|-----------|--------------------------|
| GSM-7 (standard characters) | 160 chars | 153 chars |
| Unicode (special characters, emoji) | 70 chars | 67 chars |

Credits are deducted **per part** after the message is successfully sent. For example, a 200-character standard message uses 2 parts and costs 2 credits.

---

## IP Whitelisting

If your account has IP whitelisting enabled, only requests from approved IP addresses or CIDR ranges will be accepted. Requests from unlisted IPs will receive a `403 Forbidden` response.

Contact Cast to add or update your whitelisted IPs.

---

## Sender ID

A Sender ID is the name or number displayed as the sender on the recipient's device (e.g., `MYAPP`, `BANK`, `639171234567`).

- Sender IDs must be **pre-approved** before use.
- If your account has only one Sender ID, the `sender_id` field in the request is optional — it will be used automatically.
- If your account has multiple Sender IDs, you **must** specify the `sender_id` in each request.

Contact Cast to register a Sender ID.

---

## Code Examples

### cURL — Bulk SMS

```bash
curl -X POST https://api.cast.ph/api/sms/bulk \
  -H "X-API-Key: cast_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "to": ["09171234567", "09181234567"],
    "message": "Hello from Cast!",
    "sender_id": "MYAPP"
  }'
```

### cURL — Single SMS

```bash
curl -X POST https://api.cast.ph/api/sms/send \
  -H "X-API-Key: cast_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "09171234567",
    "message": "Your verification code is 123456.",
    "sender_id": "MYAPP"
  }'
```

### JavaScript (fetch)

```js
const response = await fetch("https://api.cast.ph/api/sms/send", {
  method: "POST",
  headers: {
    "X-API-Key": "cast_your_api_key_here",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    to: "639171234567",
    message: "Your verification code is 123456.",
    sender_id: "MYAPP",
  }),
});

const data = await response.json();

if (data.success) {
  console.log("Sent! Message ID:", data.message_id, "Parts:", data.parts);
} else {
  console.error("Failed:", data.error);
}
```

### Python (requests)

```python
import requests

response = requests.post(
    "https://api.cast.ph/api/sms/send",
    headers={
        "X-API-Key": "cast_your_api_key_here",
        "Content-Type": "application/json",
    },
    json={
        "to": "09171234567",
        "message": "Your verification code is 123456.",
        "sender_id": "MYAPP",
    },
)

data = response.json()

if data["success"]:
    print(f"Sent! Message ID: {data['message_id']}, Parts: {data['parts']}")
else:
    print(f"Failed: {data['error']}")
```

### PHP (cURL)

```php
<?php

$apiKey = "cast_your_api_key_here";
$payload = json_encode([
    "to" => "639171234567",
    "message"     => "Your verification code is 123456.",
    "sender_id"   => "MYAPP",
]);

$ch = curl_init("https://api.cast.ph/api/sms/send");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "X-API-Key: $apiKey",
    "Content-Type: application/json",
]);

$response = json_decode(curl_exec($ch), true);
curl_close($ch);

if ($response["success"]) {
    echo "Sent! Message ID: " . $response["message_id"] . "\n";
} else {
    echo "Failed: " . $response["error"] . "\n";
}
```

### C# (HttpClient)

```csharp
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;

var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "cast_your_api_key_here");

var payload = JsonSerializer.Serialize(new
{
    to = "09171234567",
    message = "Your verification code is 123456.",
    sender_id = "MYAPP"
});

var content = new StringContent(payload, Encoding.UTF8, "application/json");
var response = await client.PostAsync("https://api.cast.ph/api/sms/send", content);
var body = await response.Content.ReadAsStringAsync();

using var doc = JsonDocument.Parse(body);
var root = doc.RootElement;

if (root.GetProperty("success").GetBoolean())
{
    Console.WriteLine($"Sent! Message ID: {root.GetProperty("message_id").GetString()}, Parts: {root.GetProperty("parts").GetInt32()}");
}
else
{
    Console.WriteLine($"Failed: {root.GetProperty("error").GetString()}");
}
```

---

## Support

For API access, sender ID registration, IP whitelisting, or any technical issues, contact the Cast team.