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# Inbuilt tool - send_dtmf

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The `send_dtmf` tool sends keypad tones into the active voice call. Use it when your agent has to navigate an external IVR.

## When to use

Use `send_dtmf` when your agent has called out to, or been connected to, another phone system and must press keys on the caller's behalf, for example "press 2 for billing" or entering an extension.

To collect keypad input from the caller, use [ivr\_menu](https://koreai.mintlify.site/agent-platform/inbuilt-tools/ivr-menu) or [ivr\_digit\_input](https://koreai.mintlify.site/agent-platform/inbuilt-tools/ivr-digit-input). For DTMF concepts, see [DTMF support in Artemis voice agents](https://koreai.mintlify.site/agent-platform/dtmf-support).

## Declare the tool

```yaml theme={null}
TOOLS:
  send_dtmf(
      digits: string,
      durationMs?: number,
      interDigitDelayMs?: number,
      reason?: string
  ) -> object
```

## Parameters

| Parameter | Required | Description |
| - | - | - |
| `digits` | Yes | Digits to send. Allowed characters: `0-9`, `*`, `#`. Up to 64 characters. |
| `durationMs` | No | How long each tone plays, 50 to 5000 ms. Default: 250. |
| `interDigitDelayMs` | No | Pause between tones, 50 to 5000 ms. Default: 300. |
| `reason` | No | Why the tones are sent, up to 256 characters. |

## Returns

The tool returns the number of digits sent and the tone timing it used. The digits themselves are redacted in the result and in traces, so a value such as a PIN is not exposed. An invalid entry returns an error such as `VOICE_DTMF_INVALID` and sends nothing.

## Example

```yaml theme={null}
TOOLS:
  send_dtmf(digits: string, reason?: string) -> object

FLOW:
  choose_billing:
    CALL:
      send_dtmf(digits: "2", reason: "Select billing in the external IVR")
    THEN: COMPLETE
```


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