Best 13 Tools for Building Voice AI Agents in 2025

Synthflow AI is a no-code voice automation platform that creates AI-powered phone agents for businesses. Instead of hiring more customer service staff, you can build virtual assistants that handle incoming and outgoing calls just like human employees would.

VoxImplant is a comprehensive cloud communications platform that enables businesses and developers to integrate voice, video, and messaging capabilities into their applications and services. Founded in 2013 and based in Palo Alto, the company serves millions of users worldwide through its innovative Communication Platform as a Service (CPaaS) solution.

Retell AI is an AI voice agent platform that lets businesses build, test, and deploy smart phone agents. These agents can handle both incoming and outgoing calls with human-like conversation skills and response times of under one second.

Thunai is an enterprise AI platform that converts your organization's scattered knowledge into intelligent AI agents. Think of it as creating a digital brain for your company that understands all your documents, processes, and customer interactions.

Vapi is a developer-focused platform that provides the infrastructure needed to build voice AI agents for phone interactions. Instead of spending months building voice technology from scratch, developers can use Vapi's APIs to create voice agents in minutes.

VideoSDK is a real-time communication platform that provides APIs and software tools for developers to build video and voice applications. Instead of creating video calling systems from scratch, developers can use VideoSDK's ready-made tools to add features like video meetings, live streaming, screen sharing, and AI-powered voice agents to their apps.

LiveKit is a complete real-time communication platform that uses WebRTC technology to enable low-latency audio, video, and data exchange between users and AI agents. Unlike traditional communication tools, LiveKit is built specifically for developers who want to create custom real-time experiences.

Cloudonix is a "Communications Platform as a Service" (CPaaS) that provides voice APIs, SIP trunking, and development tools for building voice applications. The platform is designed to add "superpowers" to AI voice agents by connecting them to phone systems, carriers, and business applications.

Tavus is an AI video platform that creates digital twins capable of both generating scripted videos and having real-time conversations. Think of it as your personal video clone that can speak any language, discuss any topic, and appear in unlimited videos without you ever recording again.

Cartesia AI is a real-time voice generation platform that creates human-like speech with record-breaking speed and quality. The platform is built on State Space Models (SSMs), a new type of AI architecture that processes audio much faster than traditional methods.