Wire up WhatsApp.

You will create a Worker through Cloudflare's web dashboard, paste in the code below, set five secrets, and copy the URL. About fifteen minutes.

Create the Worker

1. Open Chrome. Go to dash.cloudflare.com. Sign in.
2. In the left sidebar, click Workers & Pages. (If your account has multiple, click your account first.)
3. Click the orange Create application button. Pick the Create Worker tab.
4. Name it voice-bot. Click Deploy. Cloudflare deploys a placeholder "Hello World" worker. This is fine.
5. On the success page, click Edit code in the top right. The browser code editor opens with the placeholder code.
6. Select all the existing code (Cmd+A on Mac, Ctrl+A on Windows). Delete it.
7. Paste the code block below into the editor.
8. Click Save and Deploy in the top right. Confirm the deploy.

export default {
  async fetch(request, env) {
    if (request.method !== "POST") return new Response("OK");

    const form = await request.formData();
    const message = (form.get("Body") || "").toString();
    const from = (form.get("From") || "").toString();
    if (!message || !from) return twiml("");

    const match = message.match(/call\s+(\+\d+)\s+about\s+(.+)/i);
    if (!match) return twiml("Format: call +1xxx about <objective>");
    const [, toNumber, objective] = match;

    await fetch(
      "https://api.elevenlabs.io/v1/convai/twilio/outbound-call",
      {
        method: "POST",
        headers: {
          "xi-api-key": env.ELEVENLABS_API_KEY,
          "Content-Type": "application/json",
        },
        body: JSON.stringify({
          agent_id: env.ELEVENLABS_AGENT_ID,
          agent_phone_number_id: env.ELEVENLABS_AGENT_PHONE_ID,
          to_number: toNumber,
          conversation_initiation_client_data: {
            dynamic_variables: {
              objective,
              your_name: env.YOUR_NAME,
              agent_name: env.AGENT_NAME,
            },
          },
        }),
      }
    );
    return twiml(`${env.AGENT_NAME} is calling ${toNumber} now.`);
  },
};

function twiml(reply) {
  const body = `<Response>${reply ? `<Message>${escape(reply)}</Message>` : ""}</Response>`;
  return new Response(body, { headers: { "Content-Type": "text/xml" } });
}

function escape(s) {
  return s.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;");
}

Add the secrets

The Worker needs five values to run: your ElevenLabs API key, your Agent ID, your Phone Number ID, your name, and your agent's name.

1. Click the back arrow or breadcrumb at the top to return to the Worker overview.
2. Click Settings, then Variables and Secrets.
3. Click Add. Type variable name: ELEVENLABS_API_KEY. Paste your EL API key as the value. Set Type to Secret. Click Save.
4. Click Add again. Add ELEVENLABS_AGENT_ID with your agent ID as the value (Secret).
5. Click Add again. Add ELEVENLABS_AGENT_PHONE_ID with your phone number ID (Secret).
6. Click Add. Add YOUR_NAME with your name as a plain text variable (or Secret, your choice).
7. Click Add. Add AGENT_NAME with the name you picked for your agent.

Get the Worker URL

1. Click Overview on the Worker page.
2. Find the URL near the top. It looks like https://voice-bot.yourname.workers.dev.
3. Copy the URL.