Back to Blogs

How to add the DTMF tool to your agents

The DTMF tool lets agents send DTMF tones to an IVR phone system so that it can navigate the phone tree to it's intended goal.

Josh York, Christopher Zheng, Emanuel OliveiraJul 31, 2025
AI Agent
Outbound
Sales
DTMF
IVR

Overview

Syllable AI Agents have always been able to process DTMF inputs, but we've released a new tool that enables your agents to send DTMF signals.

The dtmf tool gives your AI Agent the power to navigate touch-tone IVRs by letting them send RFC 4733 compliant tones over the phone.

It's especially useful for outbound agents that may encounter IVRs during sales, survey and marketing calls. Since your AI Agent can already speak to voice based IVRs, this completes the toolbox for running powerful outbound AI Agents.


Step 1 – Check out the new tool

The new dtmf tool is a syllable system tool that is available to all users. Let's start by having a look.

  • Log into the Syllable Console.

  • Click the "Tools" tab.

  • Search for "dtmf".

  • Take a look at the tool schema and notice that it's interfacing directly with the Syllable System.

🛑 Tip: if you don't see the dtmf tool, you can add it by clicking creating "New tool" and copying the JSON tool definition from System Tools section of docs.syllable.ai.

Step 2 – Add the tool to your Agent's Prompt

Your agent needs access to the tool and natural language instructions on how to use it.

  • Now click on "Prompts".

  • Select the prompt that you want to update and click on "Edit".

  • In the Tools section type in "dtmf" and enable it.

  • Provide the Agent with instructions on how to use the tool inside of the prompt. As an example you can add: When asked to enter a number to reach a line, use the 'dtmf' tool to enter the number.

  • Click Save.

💡 Tip: If you're using the SDK, you can find details for updating prompts at docs.syllable.ai.


Step 3 – Test your agent

  • Now click on "Agent", select your Agent and click on "Start Session".

  • Tell the Agent to enter a digit to achieve the goal in the prompt.

  • You should see the "dtmf" tool be called in the chat window with details available in the inspector window.


Step 4 – Place an outbound call to test your agent

  • Now click on "Campaigns" and then "New Campaign".

    • Set the name, select your Agent's outbound number (channel source) and set the rate to at least 60 calls an hour.

    • Set the campaign hours and make sure they cover the time and day you'll be placing your test calls.

  • Select "Batches", "New Batch" and enable auto-run.

    • Download the CSV template, add your target IVR phone number.

    • Upload the CSV file and watch the calls light up!

  • Go to Sessions to monitor the call and verify that the agent successfully navigated the IVR.


Dive deeper into the platform in our Syllable Docs.


Missing out on the Fun?

Start building AI agents today and perfect automated outbound calls. No code required. Fully customizable. Built to scale.

Check out our demo agents

Take a look at how our agents work in real-world business use cases.