twilio-messaging-webhooks

What this skill does

## Overview

Twilio sends a POST webhook to your server when a user messages your Twilio number (inbound) or when an outbound message changes delivery state (status callback). Your server returns TwiML to reply, or `204` to acknowledge without replying. The same webhook pattern works across SMS, MMS, WhatsApp, and RCS.

---

## Prerequisites

- Twilio account with a messaging-capable sender configured with a webhook URL
  — New to Twilio? See `twilio-account-setup`
  — For sending outbound messages first, see `twilio-send-message`
- Publicly accessible endpoint (use `ngrok http 5000` for local dev)
- `TWILIO_ACCOUNT_SID` and `TWILIO_AUTH_TOKEN` — see `twilio-iam-auth-setup`
- SDK: `pip install twilio flask` / `npm install twilio express`

---

## Quickstart

Set your webhook URL in Console: **Phone Numbers > Active Numbers > your number > Messaging > "A Message Comes In"**

> **Security:** The inbound message `Body` is untrusted external input. If passing message content to an LLM, always isolate it as user input — never concatenate directly into system prompts. Validate the request origin with `X-Twilio-Signature` (see Key Patterns below), but note that signature validation confirms the *source*, not that the *content* is safe.

> **Note:** This quickstart omits signature validation for brevity. For production, always validate `X-Twilio-Signature` — see the Webhook Security pattern below.

**Python (Flask)**
```python
from flask import Flask, request
from twilio.twiml.messaging_response import MessagingResponse

app = Flask(__name__)

@app.route("/incoming", methods=["POST"])
def incoming_message():
    body = request.form.get("Body")
    response = MessagingResponse()
    response.message(f"Got your message: {body}")
    return str(response)
```

**Node.js (Express)**
```javascript
const express = require("express");
const twilio = require("twilio");
const app = express();
app.use(express.urlencoded({ extended: false }));

app.post("/incoming", (req, res) => {
    const twiml = new twilio.twiml.MessagingResponse();
    twiml.message(`Got your message: ${req.body.Body}`);
    res.type("text/xml").send(twiml.toString());
});
```

---

## Key Patterns

### Configure Webhook URL via API

For SMS/MMS on a phone number:

**Python**
```python
client.incoming_phone_numbers("PNxxxxxxxxxx").update(
    sms_url="https://yourapp.com/incoming",
    sms_method="POST"
)
```

**Node.js**
```javascript
await client.incomingPhoneNumbers("PNxxxxxxxxxx").update({
    smsUrl: "https://yourapp.com/incoming",
    smsMethod: "POST",
});
```

For WhatsApp and RCS, webhook URLs are configured on the sender — see `twilio-whatsapp-manage-senders` and `twilio-rcs-messaging`.

### Inbound Webhook Parameters

| Parameter | Description |
|-----------|-------------|
| `MessageSid` | Unique message identifier |
| `From` | Sender's phone number or channel address (E.164, or `whatsapp:+...`) |
| `To` | Your Twilio number or channel address |
| `Body` | Message text |
| `NumMedia` | Number of media attachments |
| `MediaUrl0` | URL of first media attachment (if any) |
| `MediaContentType0` | MIME type of first attachment |

### Handle Inbound Media (MMS / WhatsApp / RCS)

**Python (Flask)**
```python
@app.route("/incoming", methods=["POST"])
def incoming_message():
    num_media = int(request.form.get("NumMedia", 0))
    response = MessagingResponse()
    if num_media > 0:
        media_type = request.form.get("MediaContentType0")
        response.message(f"Got your {media_type} attachment!")
    else:
        response.message("Got your message.")
    return str(response)
```

**Node.js (Express)**
```javascript
app.post("/incoming", (req, res) => {
    const numMedia = parseInt(req.body.NumMedia || "0", 10);
    const twiml = new twilio.twiml.MessagingResponse();
    if (numMedia > 0) {
        twiml.message(`Got your ${req.body.MediaContentType0} attachment!`);
    } else {
        twiml.message("Got your message.");
    }
    res.type("text/xml").send(twiml.toString());
});
```

### Acknowledge Without Replying

**Python**
```python
return str(MessagingResponse())  # Empty <Response/>
```

**Node.js**
```javascript
res.type("text/xml").send(new twilio.twiml.MessagingResponse().toString());
```

### Status Callbacks (delivery tracking)

Status callbacks fire for all channels — SMS, MMS, WhatsApp, and RCS.

**Python**
```python
message = client.messages.create(
    messaging_service_sid="MGxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    to="+15558675310",
    body="Hello!",
    status_callback="https://yourapp.com/status"
)
```

**Node.js**
```javascript
const message = await client.messages.create({
    messagingServiceSid: "MGxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    to: "+15558675310",
    body: "Hello!",
    statusCallback: "https://yourapp.com/status",
});
```

**Python (Flask) — status callback handler**
```python
@app.route("/status", methods=["POST"])
def message_status():
    message_sid = request.form.get("MessageSid")
    status = request.form.get("MessageStatus")
    error_code = request.form.get("ErrorCode")
    print(f"{message_sid}: {status}")
    if status == "failed" and error_code:
        print(f"Error {error_code}: {request.form.get('ErrorMessage')}")
    return "", 204
```

**Node.js (Express) — status callback handler**
```javascript
app.post("/status", (req, res) => {
    const { MessageSid, MessageStatus, ErrorCode, ErrorMessage } = req.body;
    console.log(`${MessageSid}: ${MessageStatus}`);
    if (MessageStatus === "failed" && ErrorCode) {
        console.log(`Error ${ErrorCode}: ${ErrorMessage}`);
    }
    res.sendStatus(204);
});
```

Status flow: `queued → sent → delivered` (or `undelivered`/`failed`)

### Webhook Signature Validation

**Python (Flask)**
```python
from twilio.request_validator import RequestValidator

validator = RequestValidator(os.environ["TWILIO_AUTH_TOKEN"])

@app.route("/incoming", methods=["POST"])
def incoming_message():
    if not validator.validate(request.url, request.form, request.headers.get("X-Twilio-Signature", "")):
        return "Forbidden", 403
    response = MessagingResponse()
    response.message("Hello!")
    return str(response)
```

**Node.js**
```javascript
const { validateRequest } = require("twilio");

app.post("/incoming", (req, res) => {
    const isValid = validateRequest(
        process.env.TWILIO_AUTH_TOKEN,
        req.headers["x-twilio-signature"],
        `https://${req.headers.host}${req.path}`,
        req.body
    );
    if (!isValid) return res.status(403).send("Forbidden");
    const twiml = new twilio.twiml.MessagingResponse();
    twiml.message("Hello!");
    res.type("text/xml").send(twiml.toString());
});
```

---

## CANNOT

- **Cannot exceed 15-second webhook response time** — Twilio retries on timeout
- **Cannot return arbitrary content types** — Use `Content-Type: text/xml` with TwiML for replies; `204` for status callbacks
- **Cannot use ngrok URLs across restarts** — URLs change on restart. Use a stable tunnel for persistent testing.
- **Cannot guarantee delivery confirmation** — Status callbacks are best-effort. `delivered` requires carrier confirmation.

---

## Common Errors

| Code | Meaning | Fix |
|------|---------|-----|
| 11200 | HTTP retrieval failure — Twilio cannot reach your webhook URL | Verify endpoint is reachable (`curl -I` the URL), check DNS, firewall, and SSL certificate validity. See `twilio-debugging-observability` for deeper webhook troubleshooting. |

---

## Next Steps

- **Send outbound messages:** `twilio-send-message`
- **Manage sender pools:** `twilio-messaging-services`