System Prompt Design for Voice Agents
summary
Claim: system prompts change behavior dramatically — Vapi analyzes over a million calls and runs a live demo comparing three prompt strategies using OpenAI GPT4.1, Sonia and Vapi Voices. Three simulations per agent show the personality-heavy prompt fails confirmation checks repeatedly, the rigid prompt completes tasks but inflates duration and chatter, and the best-practices prompt passes confirmation gates while reducing call time and characters. Tools used: availability tool and reservation tool.
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chapters (10)
- 0:00Why Is System Prompt Design Different for Voice Agents?
- 3:14How Small Prompt Changes Affect Voice Agent Performance
- 4:44How to Design an Effective System Prompt for Voice AI
- 7:48How to Test Voice Agent Prompts With AI Simulations
- 10:27Comparing Three System Prompt Strategies for Voice Agents
- 15:40How Better Prompts Handle Ambiguity in Voice Conversations
- 17:46Which Prompt Design Produces Better Quality and Efficiency?
- 22:22How to Test and Evaluate Voice Agents Before Production
- 23:25How to Use Evals and Transcript Assertions for Voice AI Testing
- 26:28How Do You Test Voice Agents for Interruptions, Accents, and Languages?
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