> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nixflex.com/llms.txt
> Use this file to discover all available pages before exploring further.

# In-call SMS

> Text the caller while the call is happening

The `[SEND_SMS:]` tag sends a text message to the caller from your own number, during the call. Useful for addresses, links, payment links, or anything easier to read than hear.

For a text after the call ends, see [Post-call SMS](/sms/post-call-sms). For sending a message with no call involved, see [Send SMS](/sms/send-sms).

## Turning it on

In-call SMS is controlled by one setting on the agent, `incall_sms_enabled`.

| Setting | What happens                                                                                                                 |
| ------- | ---------------------------------------------------------------------------------------------------------------------------- |
| **On**  | The agent can text the caller during the call, and booking confirmations are texted automatically.                           |
| **Off** | No texts are sent at all - no mid-call text, no booking confirmation text. The agent confirms every detail out loud instead. |

With the setting off, the agent is never taught the `[SEND_SMS:]` action, so it does not offer a text. If a prompt uses the tag anyway, the engine blocks the send and the agent tells the caller the text did not go out - turn the setting on if you want texting.

New agents start with it **off**. Agents created before this setting existed were switched **on**, so their behaviour did not change.

Turn it on in the dashboard (agent, then Functions, then In-Call SMS) or through the API:

```bash theme={null}
curl -X PUT https://api.nixflex.com/v1/agents/agent_125207e452f8714a \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{ "incall_sms_enabled": true }'
```

<Note>
  This setting covers mid-call texts and booking confirmation texts only. Post-call SMS has its own setting, `post_call_sms_enabled`.
</Note>

## Syntax

\[SEND\_SMS: Your text message goes here]

Everything between the colon and the closing bracket is the SMS body. The agent continues the conversation naturally - the SMS is sent in the background.

## Example

> *Caller:* "Can you send me the address?"
>
> *Agent:* "Sure, sending it now. \[SEND\_SMS: Acme Dental, 12 High Street, Croydon CR0 1AB. See you Tuesday at 2pm.]"

## When to use

The setting grants permission; your prompt decides when and what to text. Tell the agent in its `system_prompt`, for example:

ACTIONS

* If the caller asks to receive any call information by text, send it using \[SEND\_SMS: message]
* Send the address by SMS if asked where you are: \[SEND\_SMS: 12 High Street, Croydon CR0 1AB]
* Send the payment link when collecting deposits: \[SEND\_SMS: Pay your deposit here: [https://pay.example.com/abc](https://pay.example.com/abc)]

## Booking confirmations

Booking confirmations follow the same setting. With `incall_sms_enabled` on, a confirmed booking is texted to the caller automatically - you do not need a tag in your prompt for it. With it off, the agent confirms the day, time and details out loud and no text is sent.

## Related

* [Post-call SMS](/sms/post-call-sms) - a text after the call ends
* [Send SMS](/sms/send-sms) - send a message via the API, plus length, tracking, compliance and pricing
* [SMS agent](/sms/sms-agent) - what happens when the customer texts back
* [SMS campaigns](/sms/sms-campaigns) - the same message to many numbers