Vapi

Vapi is a developer platform for building voice agents that talk to people over the phone or in a web app. It handles the parts of a live call that are hard to build yourself: streaming speech to text, sending the transcript to a language model, turning the reply into speech, and deciding when the caller has finished talking.

You pick the providers for each layer, so a team can swap the speech recognition, model or voice without rebuilding the agent. Agents can call your own API during a call to look up an order or book a slot, and Vapi can provide phone numbers or connect to an existing telephony provider.

Developers and agencies use it to build receptionists, appointment setters and support lines. Test it with real callers, accents and background noise, plan how calls transfer to a person, and check the call recording and consent rules where your callers live.