# Send SMS with Flask

Source: https://jointextkit.com/docs/send-with-flask
Index: https://jointextkit.com/llms.txt

Send a text from a Flask route with the TextKit Python SDK.

## Prompt for your AI agent

Paste this into Claude Code, Cursor or any coding agent to have it do the
integration:

```text
Add SMS sending to this Flask project with TextKit.

- Docs for this stack: https://jointextkit.com/docs/send-with-flask.md
- API: POST https://api.jointextkit.com/v1/messages with `Authorization: Bearer
  <key>` and a JSON body `{"to": "+1...", "body": "..."}`.
- Use the official SDK in your view: `pip install jointextkit`, then
  `TextKit().messages.send(to=..., body=...)`.
- Read the key from the `TEXTKIT_API_KEY` environment variable. Never hardcode
  it or send it to the browser.
- Phone numbers are E.164 and US or Canada only (`+1` followed by 10 digits).
- A test key (`ssms_sk_test_`) simulates: `+15005550006` always ends `delivered`
  and no phone gets a text.
- Errors are JSON: `{"error": {"code", "message", "param"}}` with a 4xx status.
  On `429`, wait `Retry-After` seconds and retry.
- Send only from server code that runs after a real event (a signup, an order).
  Never expose an endpoint that texts any number a visitor types.
```

## Before you start

- **An API key.** [Create a free account](/signup) and copy the test key
  (`ssms_sk_test_...`) from Home in the console. It works at once, no card.
- **Python 3.8 or later and Flask 2 or later.**
- Put the key in an environment variable:

```bash
export TEXTKIT_API_KEY=ssms_sk_test_...
```

## 1. Install

```bash
pip install flask jointextkit
```

## 2. Add a route

Create `app.py`:

```python
from flask import Flask, jsonify, request
from jointextkit import TextKit, TextKitError

app = Flask(__name__)
client = TextKit()  # reads TEXTKIT_API_KEY


@app.post("/send-sms")
def send_sms():
    data = request.get_json()
    try:
        message = client.messages.send(to=data["to"], body=data["body"])
    except TextKitError as err:
        return jsonify(error=err.code, message=str(err)), err.status
    return jsonify(id=message["id"], status=message["status"])
```

## 3. Try it

```bash
flask --app app run

curl -X POST http://localhost:5000/send-sms \
  -H "Content-Type: application/json" \
  -d '{"to": "+15005550006", "body": "Hello from TextKit"}'
```

It returns `{"id": "msg_...", "status": "delivered"}`.

> This endpoint texts whatever number it receives. Put it behind your own
> sign-in before you deploy it, or call `send` from code that runs after a real
> event (a signup, an order). An open endpoint lets anyone text through your
> account.

## What the test key did

`+15005550006` is a sandbox number: the send comes back `delivered` and no
phone gets a text (the response says `"simulated": true`). Put your own
verified phone in `to` and the test key texts it for real. See
[Sandbox & test numbers](/docs/sandbox).

## Handle errors

The SDK raises `TextKitError` with the API's `code` and `status` (plus
`param` for a bad field and `retry_after` on a rate limit). It retries network
failures and `429`s for you, with an idempotency key, so a retry never sends twice.

| Status | Code | What to do |
| --- | --- | --- |
| 400 | `invalid_request` | A field is missing or malformed; `param` names it. |
| 401 | `invalid_api_key` | The key is missing, revoked or mistyped. |
| 402 | `insufficient_credits` | Add credits; nothing was sent or charged. |
| 403 | `recipient_opted_out` | They texted STOP. Do not retry. |
| 429 | `rate_limited` | Wait `Retry-After` seconds, then retry. |

Every code is in [Errors](/docs/errors).

## Go live

1. **Add a number** in the [console](/console).
2. **Register your use case.** We file your 10DLC registration; toll-free
   numbers use a guided verification form. Until carriers approve it, the number
   texts only your verified numbers. See [Compliance & registration](/docs/compliance).
3. **Swap in a live key** (`ssms_sk_live_...`). The code stays the same.

## Next steps

- [Webhooks](/docs/webhooks): delivery receipts and replies, pushed to your server.
- [Verify](/docs/verify): one-time codes in two calls, billed only when verified.
- [Send an SMS](/docs/api/messages/send): every field the endpoint takes.
- [All quickstarts](/docs/quickstarts): the same guide for other languages and frameworks.