Vapi is a developer platform for voice AI agents, programs that hold spoken conversations with people, made by Vapi, Inc. An agent can make and receive phone calls or run inside a web application.
Every Vapi assistant chains three models: speech-to-text turns the caller's words into text, a large language model (an AI model that reads and writes text) decides the reply, and text-to-speech speaks it. The builder picks each part from many providers, such as Deepgram, OpenAI, Anthropic and ElevenLabs. Assistants can call outside APIs and databases as tools, and Squads join several specialized assistants with transfers between them. Vapi supplies phone numbers and connects to telephony providers such as Twilio. Agents are set up in a dashboard or through the API, SDKs and a command-line tool, and they can be tested with simulated calls before going live.
It is a hosted service billed per minute of calls: a Vapi hosting fee plus the model providers' costs passed through without markup. Optional monthly success packages add support and capacity.