Voice AI Agents

Every call answered. Instantly.

AI voice agents that answer calls, book appointments and qualify leads in natural conversation — and pass the call to a person when needed. Free working prototype in 1 day, then a production release at a fixed price and date.

Realtime voiceTwilioElevenLabs

Get your free prototype 30-min call · no commitment

9:41

Smile Dental · incoming

Bella

AI receptionist · 01:24

CallerHi, can I book a cleaning for Thursday?

Bella · AISure! I have 10:30 or 15:00 on Thursday. Which suits you?

Caller15:00, please.

Bella · AIBooked ✓ You'll get a text confirmation.

receptionist.pyAI

agent = VoiceAgent(

voice="bella", language="en",

tools=[check_slots, book, transfer_to_staff],

greeting="Smile Dental, this is Bella!",

)

phone.route("+44 20 …", to=agent)

Senior review · approved

Pipelinemain

Buildvoice + tools
Test calls200 passed
Senior review
Pilotafter hours
Production24/7

Buildto launch

Day 1Week 1Week 2Week 3Live

Bella is answering callsSmile Dental · 24/7now

At a glance

One product. One price, one date.

The essentials, before you book a call.

UDEX builds Voice AI Agents for founders and product teams. AI voice agents that answer calls, book appointments and qualify leads in natural conversation — and pass the call to a person when needed. AI writes the code, tests and CI/CD, while senior engineers own the architecture and review every change.

1 dayFree prototypeNo payment, no commitment

FixedPrice and dateAgreed before we start

100%YoursCode, repository and accounts

Platform: Phone and in-app voice agents
Ships to: Production
Stack: OpenAI RealtimeTwilioDeepgramElevenLabsPython
Quality: Senior review on every change, automated tests, CI/CD

How it works

Idea to production. In three steps.

AI does the heavy lifting. Senior engineers make every decision that matters.

01Day 0
Share the idea
A 30-minute call. We agree on the core flow, the scope and a fixed release date.
02Day 1 → release
AI builds, senior engineers decide
AI writes the code, tests and CI/CD. Senior engineers set the architecture and review every change. Your prototype is ready on day 1.
03Release day
Ship to production
The release goes live, and the code, repository and accounts are handed to you.

Who it’s for

Built for founders and product teams.

Here is where it works best, and where it doesn’t.

Clinics and salons

Bookings and reschedules handled on the phone, 24/7.

Service businesses

Qualify leads and book visits while your team works.

Support lines

Resolve common requests and route the rest.

Restaurants and hospitality

Reservations and questions without hold music.

Sales teams

Follow-up calls and qualification at scale.

Apps and devices

Natural voice control inside your product.

Not the right fit

Calls that must legally be handled only by licensed staff.
Outbound cold-calling campaigns.
Certified compliance from day one, such as HIPAA or PCI audits.
Open-ended research without a defined first release.

How we work

Six stages, one team.

All services

Pricing

Start free. Ship at a fixed price.

Two steps. The prototype costs nothing, and the release costs exactly what we agree.

Prototype

Free1 day

A working prototype of your core flow to test with users and show investors.

Key screens and the main user flow
Working on real devices and browsers
No payment, no commitment

Get the free prototype

Release

Fixed priceand date, agreed upfront

A production release, shipped to production, that you fully own.

OpenAI Realtime, Twilio, Deepgram and the features agreed on the call
Automated tests, CI/CD and senior code review
Release to production and 100% code ownership

Start with a call

Fixed means fixed. No hourly billing and no surprise invoices: anything new is priced before it is built.

Book a call

Thirty minutes. Then your prototype.

Walk us through the idea, and we will scope the core flow and build your free prototype the next day.

Book a 30-min call

FAQ

Questions, answered.

Straight answers about cost, timing, quality and ownership.

How much does it cost to build a Voice AI Agent?

The price is fixed for the agreed scope and set before work starts. You first get a free working prototype of the core flow in 1 day, then a fixed price and release date for the production version.

How long does it take to build a Voice AI Agent?

A working prototype takes 1 day. The production release date is agreed upfront and depends on the scope; AI speed with senior engineering makes it much faster than classic development.

Does it sound natural?

Yes. Low-latency voice with natural pauses, interruptions and your choice of voice and language.

What happens with difficult calls?

The agent transfers the call to a person with a short summary, so the caller never repeats themselves.

Can it use our booking system?

Yes. It checks availability and books, changes or cancels appointments through your system's API.

Is the prototype really free?

Yes, with no commitment. After a 30-minute call we build a working prototype of your core flow in 1 day, and then you decide whether to continue to the release.

Will the price go up during the build?

No. The price is fixed for the agreed scope. Anything new you want to add mid-build is priced separately and built only after you approve it.

Who owns the code?

You do, 100%. The source code, repository and accounts are yours, and the release ships to production under your name.

Is AI-written code safe to ship to production?

It ships only after senior review. Senior engineers own the architecture, security and code quality, and automated tests run on every change.

In practice