Vapi

Vapi is a developer platform for building, testing, and deploying voice AI applications — phone-based agents that handle inbound and outbound calls with near-human latency. The core challenge in voice AI is latency: users expect under 500ms response times, and stitching together speech-to-text, LLM inference, and text-to-speech yourself produces delays that make conversations feel broken. Vapi handles the entire stack — STT, LLM routing, TTS, interruption handling, and call management — with sub-second response times out of the box. Teams use it to build appointment booking bots, customer service agents, sales dialers, and intake systems that operate at scale without human agents. Free to start with usage-based pricing.