Nixflex - AI Voice Platform for Building AI Phone Agents

Web calls let a visitor speak to your AI agent directly from a web page, using their microphone. Same agent, same prompt, same tools and booking - but the audio travels over the internet instead of a phone line. No carrier minutes are used, and it works from any country with zero telephony setup.

A web call is an inbound call to the number’s agent. It appears in call history, is recorded, analysed, billed, and fires webhooks exactly like a phone call. The caller shows as web.

Enabling web calls on a number

Web calls are off by default on every number. Turn them on per number:

curl -X PUT https://api.nixflex.com/v1/integrations/web-calls/number/+441234567890 \
  -H "Authorization: Bearer YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"enabled": true}'

GET the same path to read the flag, DELETE to force it off. Turning the flag off is the kill switch - every start request for that number is refused from that moment.

Pricing

Calls on a number with web calls enabled bill at **

0.09 per minute** - the same rate as [Live Monitor](/concepts/live-monitor). The two switches are independent, but the price is one rule: **either** feature enabled on a number means that number's calls bill at

0.09/min. Both enabled is still $0.09 - never more. Web calls use no carrier, so there are no Twilio/Telnyx charges at all on these calls.

Starting a call from your own page

The start endpoint is public - the number is the identity. No API key ever reaches the browser; the engine verifies the flag, the owner’s balance, the agent, and concurrency on every single request.

POST https://api.nixflex.com/web-call/start
Content-Type: application/json

{"number": "+441234567890"}

Success returns the visitor’s audio credentials:

{
  "ok": true,
  "call_id": "WEB...",
  "livekit": { "url": "wss://...", "token": "...", "room": "webcall-WEB..." }
}

Join with livekit-client, publish the microphone, and the agent answers:

const room = new LivekitClient.Room();
await room.connect(res.livekit.url, res.livekit.token);
room.on(LivekitClient.RoomEvent.TrackSubscribed, (track) => {
  if (track.kind === 'audio') document.body.appendChild(track.attach());
});
await room.localParticipant.setMicrophoneEnabled(true);

Ask for microphone permission before calling the start endpoint. If you start the call first, the agent greets while your visitor is still looking at the permission popup.

A refused start returns {"ok": false, "reason": "..."} - unavailable (number unknown, feature off, or owner unfunded), busy (concurrency cap), or bad_number.

Behaviour and guarantees

Inbound only. A web call always rings in to the number’s agent.
Everything is inherited. Voice, prompt, language, booking tools, custom functions, transfers, webhooks, post-call analysis - whatever the number’s agent does on the phone, it does on the web.
Interruptions work. Visitors can talk over the agent and it stops, like a phone call.
Recording included. If recording is on for the number/agent, web calls are recorded - and an interrupted sentence is recorded only up to the moment it was cut, exactly as the visitor heard it.
Caller identity is web. Every visitor arrives as the same caller, so caller history and greet-by-name are deliberately skipped on web calls.
No SMS destination. A browser visitor has no phone number, so [SEND_SMS] and booking confirmation texts cannot be delivered. Tell your agent in its prompt not to offer texts on web calls - or have it collect a mobile number first.

Web Agent widget - the embeddable Call + Chat launcher
Live Monitor - listen to calls live at the same $0.09 rate

Get started

Core concepts

In-call actions

Features

SMS

Reference

Web Calls

Enabling web calls on a number

Pricing

Starting a call from your own page

Behaviour and guarantees

​Enabling web calls on a number

​Pricing

​Starting a call from your own page

​Behaviour and guarantees

​Related

Enabling web calls on a number

Pricing

Starting a call from your own page

Behaviour and guarantees

Related