twilio-communications

What this skill does

# Twilio Communications

Build communication features with Twilio: SMS messaging, voice calls,
WhatsApp Business API, and user verification (2FA). Covers the full
spectrum from simple notifications to complex IVR systems and multi-channel
authentication. Critical focus on compliance, rate limits, and error handling.

## Patterns

### SMS Sending Pattern

Basic pattern for sending SMS messages with Twilio.
Handles the fundamentals: phone number formatting, message delivery,
and delivery status callbacks.

Key considerations:
- Phone numbers must be in E.164 format (+1234567890)
- Default rate limit: 80 messages per second (MPS)
- Messages over 160 characters are split (and cost more)
- Carrier filtering can block messages (especially to US numbers)

**When to use**: Sending notifications to users,Transactional messages (order confirmations, shipping),Alerts and reminders

from twilio.rest import Client
from twilio.base.exceptions import TwilioRestException
import os
import re

class TwilioSMS:
    """
    SMS sending with proper error handling and validation.
    """

    def __init__(self):
        self.client = Client(
            os.environ["TWILIO_ACCOUNT_SID"],
            os.environ["TWILIO_AUTH_TOKEN"]
        )
        self.from_number = os.environ["TWILIO_PHONE_NUMBER"]

    def validate_e164(self, phone: str) -> bool:
        """Validate phone number is in E.164 format."""
        pattern = r'^\+[1-9]\d{1,14}$'
        return bool(re.match(pattern, phone))

    def send_sms(
        self,
        to: str,
        body: str,
        status_callback: str = None
    ) -> dict:
        """
        Send an SMS message.

        Args:
            to: Recipient phone number in E.164 format
            body: Message text (160 chars = 1 segment)
            status_callback: URL for delivery status webhooks

        Returns:
            Message SID and status
        """
        # Validate phone number format
        if not self.validate_e164(to):
            return {
                "success": False,
                "error": "Phone number must be in E.164 format (+1234567890)"
            }

        # Check message length (warn about segmentation)
        segment_count = (len(body) + 159) // 160
        if segment_count > 1:
            print(f"Warning: Message will be sent as {segment_count} segments")

        try:
            message = self.client.messages.create(
                to=to,
                from_=self.from_number,
                body=body,
                status_callback=status_callback
            )

            return {
                "success": True,
                "message_sid": message.sid,
                "status": message.status,
                "segments": segment_count
            }

        except TwilioRestException as e:
            return self._handle_error(e)

    def _handle_error(self, error: TwilioRestException) -> dict:
        """Handle Twilio-specific errors."""
        error_handlers = {
            21610: "Recipient has opted out. They must reply START.",
            21614: "Invalid 'To' phone number format.",
            21211: "'From' phone number is not valid.",
            30003: "Phone is unreachable (off, airplane mode, no signal).",
            30005: "Unknown destination (invalid number or landline).",
            30006: "Landline or unreachable carrier.",
            30429: "Rate limit exceeded. Implement exponential backoff.",
        }

        return {
            "success": False,
            "error_code": error.code,
            "error": error_handlers.get(error.code, error.msg),
            "details": str(error)
        }

# Usage
sms = TwilioSMS()
result = sms.send_sms(
    to="+14155551234",
    body="Your order #1234 has shipped!",
    status_callback="https://your-app.com/webhooks/twilio/status"
)

### Anti_patterns

- Not validating E.164 format before sending
- Hardcoding Twilio credentials in code
- Ignoring delivery status callbacks
- Not handling the opted-out (21610) error

### Twilio Verify Pattern (2FA/OTP)

Use Twilio Verify for phone number verification and 2FA.
Handles code generation, delivery, rate limiting, and fraud prevention.

Key benefits over DIY OTP:
- Twilio manages code generation and expiration
- Built-in fraud prevention (saved customers $82M+ blocking 747M attempts)
- Handles rate limiting automatically
- Multi-channel: SMS, Voice, Email, Push, WhatsApp

Google found SMS 2FA blocks "100% of automated bots, 96% of bulk
phishing attacks, and 76% of targeted attacks."

**When to use**: User phone number verification at signup,Two-factor authentication (2FA),Password reset verification,High-value transaction confirmation

from twilio.rest import Client
from twilio.base.exceptions import TwilioRestException
import os
from enum import Enum
from typing import Optional

class VerifyChannel(Enum):
    SMS = "sms"
    CALL = "call"
    EMAIL = "email"
    WHATSAPP = "whatsapp"

class TwilioVerify:
    """
    Phone verification with Twilio Verify.
    Never store OTP codes - Twilio handles it.
    """

    def __init__(self, verify_service_sid: str = None):
        self.client = Client(
            os.environ["TWILIO_ACCOUNT_SID"],
            os.environ["TWILIO_AUTH_TOKEN"]
        )
        # Create a Verify Service in Twilio Console first
        self.service_sid = verify_service_sid or os.environ["TWILIO_VERIFY_SID"]

    def send_verification(
        self,
        to: str,
        channel: VerifyChannel = VerifyChannel.SMS,
        locale: str = "en"
    ) -> dict:
        """
        Send verification code to phone/email.

        Args:
            to: Phone number (E.164) or email
            channel: SMS, call, email, or whatsapp
            locale: Language code for message

        Returns:
            Verification status
        """
        try:
            verification = self.client.verify \
                .v2 \
                .services(self.service_sid) \
                .verifications \
                .create(
                    to=to,
                    channel=channel.value,
                    locale=locale
                )

            return {
                "success": True,
                "status": verification.status,  # "pending"
                "channel": channel.value,
                "valid": verification.valid
            }

        except TwilioRestException as e:
            return self._handle_verify_error(e)

    def check_verification(self, to: str, code: str) -> dict:
        """
        Check if verification code is correct.

        Args:
            to: Phone number or email that received code
            code: The code entered by user

        Returns:
            Verification result
        """
        try:
            check = self.client.verify \
                .v2 \
                .services(self.service_sid) \
                .verification_checks \
                .create(
                    to=to,
                    code=code
                )

            return {
                "success": True,
                "valid": check.status == "approved",
                "status": check.status  # "approved" or "pending"
            }

        except TwilioRestException as e:
            # Code was wrong or expired
            return {
                "success": False,
                "valid": False,
                "error": str(e)
            }

    def _handle_verify_error(self, error: TwilioRestException) -> dict:
        """Handle Verify-specific errors."""
        error_handlers = {
            60200: "Invalid phone number format",
            60203: "Max send attempts reached for this number",
            60205: "Service not found - check VERIFY_SID",
            60223: "Failed to create verification - carrier rejected",
        }

        return {
            "success": False,
            "error_code": error.code,
            "error": error_handlers.get(error.code, error.msg)
        }

# Usage Example - Signup Flow
verify