Five9

Five9's AI Agent Studio lets you build voice agents with built-in reasoning, tool calling (so agents can query databases, APIs, and business systems), and safety guardrails to keep the agent on script. You define the agent's goals and tools in a visual interface, and the AI reasons about which tools to call and when, handling multi-step workflows without you choreographing every branch. It runs on Five9's cloud contact center infrastructure.

The platform is designed for large contact centers replacing or augmenting live agents. Tool calling is a key differentiator, letting your voice agent actually accomplish things (transfer funds, update records, schedule appointments) without waiting for human handoff. The learning curve is moderate, and pricing scales with usage. If you're running a high-volume contact center and want your voice agents to solve problems autonomously, Five9 is worth a close look.