Vapi is an advanced AI voice-agent platform designed to help developers and businesses create natural-sounding voice assistants for real-time phone calls, customer support, sales, appointment booking, and conversational automation. Its API gives developers a simple way to integrate intelligent voice agents into apps, websites, or phone systems without needing custom speech-to-text, text-to-speech, or telephony infrastructure. Vapi supports high-quality AI voice models, custom personalities, memory, streaming responses, and real-time conversations using LLMs such as GPT-4.1, GPT-5, Claude, and more. Agents can make outbound calls, receive inbound calls, gather user information, follow complex workflows, and integrate with CRMs, databases, or custom business logic. The platform includes tools like custom voice cloning, call logs, multi-turn conversation handling, and webhooks for automating processes. It offers a freemium model with pay-as-you-go pricing for minutes used, making it suitable for startups, support teams, and developers building AI-driven phone experiences.