AI voice agent platform for business phone calls
An AI voice agent platform is the software where you build an AI agent, connect it to a phone line and read what happened on every call. Stemvo is a voice AI platform built in the EU: you describe the business in plain words, forward your own number and pay €0.09 a minute, all-in, for a standard-size agent.
What the Stemvo platform includes
Everything below is in the dashboard today and included in the per-minute price.
Agent builder in plain words
Write what the business does, its services and how the agent should greet callers. No flow charts and no code.
Knowledge from your website
The platform reads your website and keeps the agent’s knowledge up to date.
Voices in 10 languages
Each agent speaks the language you set for it, in one of 10 languages, with GPT-5.1 as standard.
Incoming and outgoing calls
The agent answers your line and can also call people, for example to return enquiries.
Your own functions
During a call the agent can call your HTTP endpoints, for example to look up an order or open a ticket.
A summary of every call
A summary of every call in your dashboard and by webhook, and by e-mail if you switch it on for the agent. You choose extra fields to pull out of each call.
Transcripts and recordings
Recordings are kept 30 days and transcripts 180 days by default. You can set anything from 1 to 730 days.
Team access
Owner and member roles, with optional two-factor login (a code from an authenticator app).
White label for agencies
Client accounts under your logo and your own price per client. See white label voice AI.
What happens on a call
Example: a caller rings a dental practice at lunchtime.
| Step | What the caller hears or does | What you see afterwards |
|---|---|---|
| The call comes in | Dials the practice’s usual number, which forwards to the agent. | Time, number and length of the call |
| Greeting | Hears the practice’s name and that they are speaking with an AI. | The full transcript |
| Questions | Asks about opening hours and the price of a check-up and gets the answer. | Analysis fields you choose |
| Message | Leaves their name, number and a request for an appointment. | A summary with the request and the callback number |
Example call. The practice is fictional.
How to choose the best AI voice agent platform
Seven things to check on any platform before you build on it.
| What to check | Why it matters | On Stemvo |
|---|---|---|
| The full price per minute | Some platforms list a platform fee and bill the AI model, speech recognition and voice on top. | €0.09 a minute, all-in, for a standard-size agent |
| Where call data is stored | Your customers’ calls are personal data under the GDPR. | Servers in Germany; sub-processors listed in the DPA |
| Languages | Callers expect to be answered in their own language. | 10 languages, one per agent |
| Your own number | Callers keep dialling the number they already know. | Forward your number or connect your SIP account |
| Setup time | A platform that needs a developer for every change slows you down. | Plain-words builder and test calls in your browser |
| API and webhooks | Call data should reach your CRM or helpdesk. | REST API and signed webhooks |
| Contract | A long contract locks you in before you know the results. | Prepaid balance, no monthly fee, no setup fee |
If you use Vapi today, Vapi pricing compared with Stemvo shows what a month costs on each.
Price of the Stemvo voice AI platform
€0.09 a minute, all-in. For a standard-size agent. Bigger agents see their exact price in the dashboard before going live.
- GPT-5.1 as standard, speech recognition, voice and platform included
- No monthly fee, no setup fee
You top up a prepaid balance by bank transfer (SEPA), from €20. Calls are paid from that balance; there is no card payment and no monthly bill. You set a daily spending limit and get a warning before you reach it.
Start with €5 freeDrag to your number of call minutes. Prices excl. VAT, for a standard-size agent. Your phone provider bills your number and line as before.
Connect your own phone number
Landline or office number
Use your own number: forward it to your agent or connect your provider’s SIP account. The dashboard has guides for sipgate, Telekom, Voys and Zadarma.
Only a mobile number
A mobile can forward calls to a normal phone number, but not to your agent directly. Take a low-cost virtual number in your own name from a phone provider, for example sipgate or easybell, connect it to your agent and forward your mobile to it.
Only the calls you miss
You can set forwarding to switch on only when nobody answers or the line is busy. Your team takes the calls it can, and the agent takes the rest.
Voice AI platform API for developers
List agents and calls, start outbound calls, read recordings, delete calls, read appointments and your balance. Signed webhooks report call.started, call.ended and call.analyzed. Creating and editing agents over the API comes later. Details on the voice AI API page.
curl https://api.stemvo.eu/api/v1/calls \
-H "Authorization: Bearer $STEMVO_API_KEY" \
-d '{"agent_id":"…","to":"+31…","variables":{}}'AI voice agent platform questions
What is an AI voice agent platform?
It is the software for building AI agents that answer and make phone calls. You write the agent’s instructions, connect a phone line, and the platform runs speech recognition, the AI model and the voice on every call, then stores the transcript and summary.
Is a voice AI platform the same thing?
Yes. People use both names for software that runs AI phone agents. Some voice AI platforms only offer an API for developers; Stemvo has a dashboard for businesses and agencies and an API for developers.
How much does the Stemvo platform cost?
€0.09 a minute, all-in, excl. VAT, for a standard-size agent. Bigger agents see their exact price in the dashboard before going live. There is no monthly fee and no setup fee.
What is a standard-size agent?
Size means the length of your agent’s instructions, services and functions. The dashboard shows the price per minute before you publish the agent.
Can I try it for free?
Yes. €5 free once per business, about 55 minutes, valid 30 days, no card needed. Stemvo is sold to businesses only.
Where is call data stored?
Stored on servers in Germany. Speech recognition and the AI model run at sub-processors, some in the USA, listed in our data processing agreement.
Can I move my agents from another platform?
Yes. Copy your prompt and knowledge into a Stemvo agent, test both side by side, then switch your call forwarding.
Build your first AI voice agent
€5 free once per business, about 55 minutes, valid 30 days, no card needed.
Build your agent