Vapi.ai

Vapi.ai is a developer platform for building voice AI agents that handle phone calls instead of a person. It is built by the company of the same name and has become one of the most widely used tools in its category. It is designed for developers, startups, agencies, and businesses that want to automate calls in customer support, sales, or booking without building an entire telephony stack from scratch.

It works like a building kit: you define how the agent should speak, its script and voice, then connect it to a phone number and your systems. The agent listens to the caller in real time, understands them, and replies in a natural voice — handling both inbound and outbound calls. You can monitor, record, and evaluate every call, so over time you see what works and keep improving the agent.