Vapi AI is a voice automation platform designed for developers to build, test, and deploy advanced voice AI agents for phone calls and web applications. It operates through a real-time pipeline of speech-to-text, language model processing, and text-to-speech, with support for multiple providers including Deepgram, OpenAI, Claude, ElevenLabs, and Play.ht. The platform offers a visual Flow Studio builder for designing conversational logic, tool calling and webhook routing for backend integration, agent chaining via Squad architecture for multi-agent orchestration, and support for over 100 languages. Developers can customize every aspect of the conversation flow, from voice tone and speaking speed to interrupt handling and emotion detection, with real-time responsiveness typically between 550-800 milliseconds.