Custom No-Code Voice Agent Automation Powered by GPT-4o

Retell AI built an AI-native no-code platform to replace legacy call scripting systems. This platform creates natural voice agents capable of answering questions, managing reservations, and handling administrative tasks, and it operates without hold music or complex engineering.

By integrating GPT-4o, Retell has been able to deliver new features to customers within days. In particular, the function calling capability allows agents to handle bookings, lead generation, and administrative issues in real time, with human-like reasoning and response abilities.

Since adopting GPT-4o, behaviors can now be defined simply through the UI, without complex prompt engineering or hardcoding. By leveraging GPT-4o's native function calling interface, Retell achieved a success rate of over 70% in multi-turn function calling, roughly 2x higher than with previous models.

With GPT-4o, Retell has launched the following new features:

• Post-call analysis and outcome evaluation
• Agent workflows configurable with minimal prompt engineering
• Dynamic conversation flows such as objection handling and multi-slot booking

This approach is translating into tangible results. Teams using Retell have cut call handling costs by up to 80% and are achieving performance on par with human agents, recording a CSAT of over 85%.