Vapi

What it does

Vapi stitches speech-to-text, a model and text-to-speech into a voice agent you configure in a dashboard, then handles SIP trunks, latency and interruption logic. It is infrastructure, not a chatbot builder.

Latency is the whole game: under a second feels human, two seconds feels broken. Test on real phone lines in the countries you sell to, not in the browser.

Standout features

• Inbound and outbound calls
• Interruption handling
• Swap models and voices
• Webhook tool calls

Best for