Make an Outbound Voice Call by Asking Claude

Introduction

I’ve shown you how the Vonage Tooling MCP Server can be accessed via Postman. In today’s blog post, I’ll show you how to access it via Claude Desktop, and the use case I’ll focus on is to trigger a real outbound voice call using the same way you might communicate with LLMs, some natural language prompt. We’ll use Claude Desktop, create a Vonage account, get some API keys, add them to Claude, and see everything in action.

Prerequisites

Before we get started and place that phone call, you'll need:

• Claude Desktop installed

• Node.js installed

• A Vonage account

Select the “Voice” under Capabilities, as we are going to use the voice API to make calls.

Click to save your newly created Vonage application with the voice capability at the bottom right.

Add the Vonage Tooling MCP Server to Claude Desktop

Open Claude Desktop and on the settings tab, click on “developer” and click on “edit config”. This will take you to your “claude_desktop_config.json”, but you can also open it directly, as shown below:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json, which usually resolves to something along the lines of C:\Users\username\AppData\Local\Packages\Claude\LocalCache\Roaming\Claude

{

  "mcpServers": {

    "vonage-tooling": {

      "command": "npx",

      "args": [

        "-y",

        "@vonage/vonage-mcp-server-api-bindings"

      ],

      "env": {

        "VONAGE_API_KEY": "YOUR_API_KEY",

        "VONAGE_API_SECRET": "YOUR_API_SECRET",

        "VONAGE_APPLICATION_ID": "YOUR_APP_ID",

        "VONAGE_PRIVATE_KEY64": "YOUR_BASE64_PRIVATE_KEY",

        "VONAGE_VIRTUAL_NUMBER": "+1234567890"

      }

    }

  }

}

Note: VONAGE_PRIVATE_KEY64 is your private key file base64-encoded. On macOS/Linux, you can generate it with base64 -i private.key | tr -d '\n' . I wanted to copy it to my clipboard whilst doing this on GitHub Codespaces, and I used the following command: base64 -i private.key | tr -d '\n' > b64_key.txt && code b64_key.txt to copy it to a new txt file, but you can use | pbcopy on macOS to copy it to your clipboard.

Save the file and don’t forget to restart Claude Desktop, so that everything you’ve added is applied. You should see the Vonage tools appear in the Connectors tab of the settings. Make sure to give permission to the “Outbound Voice Message” tool.

Tools Permissions

Make the Outbound Voice Call

Now that the setup is done, open a new conversation in Claude Desktop and type something along the lines of: "Use the Vonage outbound voice message tool to call +44XXXXXXXXX and say: Hello, this is a test call from Claude."

Claude will identify the outbound-voice-message tool from the Vonage Tooling MCP, which maps directly to the Vonage Voice API under the hood. The MCP server handles authentication and the API call; you just described what you wanted in plain English. It confirms the parameters and places the call.

Your phone rings and speaks the message using text-to-speech. You can try writing a different text that you would like to be spoken from the text.

Claude Conversation

Conclusion

Why not try the other Tools with Claude? Check your account balance before placing the call, list your applications and numbers to pick the right one, send an SMS follow-up after the call, all with the same natural language prompting.

It’s pretty cool what we can do with Claude Desktop and the Vonage MCP Servers. In my next blog post, I’ll show how you can interact with the Vonage MCPs using Google Antigravity. Stay tuned.