Vonage

Vonage, formerly Nexmo, combines a Communications API platform with AI Studio, a visual builder for voice agents. You define agent logic using flowcharts, wire in prompts and knowledge bases, then connect to Vonage's voice infrastructure. The platform also covers SMS, video, and messaging if you want to expand beyond voice later.

Suitable for enterprises and mid-market organizations wanting a unified communications platform with voice agents as part of a broader ecosystem. Vonage's depth works well when you need agent callbacks, escalations, and tight integrations with existing communications workflows.