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BigTree108

Voice AI agent development services

Voice AI agent development: phone agents and AI receptionists that answer calls, book appointments, qualify leads and route callers, in-app voice assistants, outbound reminder and follow-up calls, and call transcription and analytics, built on the OpenAI Realtime API, Gemini Live, ElevenLabs, Deepgram and Cartesia, on Vapi, Retell AI, LiveKit or Pipecat, connected to your telephony, calendar and CRM, with dedicated voice AI developers for your team or a voice agent delivered end to end.

Voice agents we build

  • Phone agents and AI receptionists

    Agents that answer every call, book appointments in your calendar, answer questions from your content, take messages and transfer to a person by rule, with a summary of each call logged in your CRM.

  • Outbound calls

    Appointment reminders, confirmations, follow-ups and surveys, with calling hours, consent and do-not-call rules enforced in code, and every call recorded and summarised.

  • In-app voice assistants

    Voice in your web or mobile app that understands the user, acts on their data and answers aloud, streamed over WebRTC with low latency.

  • Telephony integration

    Twilio, Telnyx, Vonage, SIP trunks and existing contact-centre platforms connected, with call transfer, voicemail detection, and recordings stored where your policy says.

  • Speech and voices

    Speech recognition tuned to your vocabulary and accents, natural voices from ElevenLabs, Cartesia or OpenAI, and calls in several languages, Ukrainian included.

  • Latency and turn-taking

    Speech-to-speech models, or a streamed pipeline of speech recognition, a language model and text-to-speech, tuned for response time, interruptions and natural turn-taking.

  • Call analytics

    Calls transcribed, summarised and labelled by topic, sentiment and outcome, with quality checks that used to need a person listening.

  • Testing with simulated callers

    Hundreds of scripted and adversarial calls run against every release, so a change to a prompt, model or voice is measured before a customer hears it.

  • Disclosure and consent

    Callers told they are speaking with an AI, consent taken for recording, call data kept only as long as your policy allows, and card details kept out of transcripts.

Hire voice AI developers

  • Dedicated voice AI developers

    Voice AI developers who join your team full time, work in your tools and process, and report to your lead. You interview them; we carry the Ukrainian contract, payroll, invoicing and leave.

  • Voice AI development projects

    A defined piece of voice AI development with a scope, a fixed plan and a named lead on our side who owns the result and reports progress in your channels.

  • Ongoing voice AI development

    Voice AI development as a continuing service: the same people every month, a backlog you prioritise, and hours you can see in our portal and on the invoice.

The dedicated team page explains how specialists join your team, and the outsourcing page covers project delivery, take-overs and how we charge.

Who works on your voice AI development

  • Voice AI developers

    Realtime models, speech pipelines and voice platforms

  • Backend engineers

    Telephony, calendar and CRM integrations

  • Front-end and mobile engineers

    Voice in web and mobile apps

  • Content writers

    Call scripts, prompts and hand-off rules

  • QA engineers

    Simulated calls and regression tests

Voice agents callers stay on the line with

On the phone, half a second of silence feels long. We measure response time, interruptions and transfers on every build, choose between speech-to-speech models and a streamed pipeline by what your calls need, and test with simulated callers before real ones.

The agent says it is an AI, transfers to a person by clear rules and never takes card details by voice. Recordings and transcripts are kept only as long as your policy allows.

Other AI development services we provide

AI development overview

Questions about voice AI agents

Vapi, Retell AI or a custom build?

A platform such as Vapi or Retell AI is the quickest way to a working phone agent and suits most receptionist and booking work. A custom build on LiveKit or Pipecat gives more control over cost per minute, data location and behaviour at scale. We build on either and can move you from one to the other.

What does a minute of an AI call cost?

It depends on the speech, model and telephony providers you choose. We estimate the cost per minute from your call volumes before the build and log the real figure for every call afterwards.

Can the agent speak Ukrainian, German or Spanish?

Yes. Current speech models and voices handle most European languages, and the agent can follow the caller into another language. Each language gets its own test calls before launch.

How quickly can voice AI developers start?

When the right voice AI developer is available, the start is gated only by your interview and the NDA and IP assignment. Otherwise we run a search, which typically produces candidate profiles within two to three weeks, and nobody starts until you have said yes.

How do we hire voice AI developers through BigTree108?

Tell us the work, the seniority and the hours you need. We propose one or two people with their profiles, you interview them the way you would interview your own hire, and you sign one agreement with BIG TREE 108 LLC and receive one invoice a month.

Who owns the work they produce?

You do. Every specialist has a signed contract with BigTree108 that assigns all work product to the company, and our agreement with you assigns it onward. Code, designs and documents are delivered into your own repositories and tools, not kept where only we can change them.

Want an agent to answer your phones?

Tell us the calls you get, the systems behind them and your volumes. You get an answer within one business day: a plan, a cost per minute estimate, or candidate profiles.

Email hello@bigtree108.com How we respond