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Creating Your AI Persona

The most important part of your AI agent is the instructions (system prompt). This defines who the agent is, what they do, and how they behave.

Writing Effective Instructions

Your instructions should include:

1. Identity & Role

2. Goal & Context

3. Tone & Style

4. Handling Scenarios

5. Boundaries

Complete Example

Voice Selection

Realtime Mode Voices

In Realtime Mode, choose from preset voices optimized for low-latency conversations. The default voice is alloy. Check available voices via GET /v1/voices/builtin.
Realtime Mode voices are optimized for ultra-low latency and natural conversation. They work best for English but can handle other languages with proper instructions.

Legacy Mode: Full Voice Library

Legacy Mode gives you access to hundreds of built-in voices plus voice cloning:
  • Large voice library with voices across different styles and tones
  • Voice cloning: Upload audio samples to clone any voice
  • Multiple languages supported
  • Custom voice IDs: Use any voice from our library
Check available voices via GET /v1/voices/builtin and GET /v1/voices.

Language & Dialect Control

Realtime Mode

  • Auto-detection: Works automatically but best with explicit instructions
  • Instruction-based: Tell the AI “Speak only in Spanish” or “Respond in French”

Legacy Mode

  • Full control: Set stt_language for speech recognition
  • 36+ languages: en-US, en-GB, en-AU, es-ES, es-MX, fr-FR, de-DE, and more
  • Dialect-specific: Choose British English (en-GB) vs American (en-US)

Temperature & Creativity

Control how creative or focused your AI is:
  • 0.0-0.3: Very focused, consistent responses (good for confirmations)
  • 0.4-0.7: Balanced (default, good for most use cases)
  • 0.8-1.0: Creative, varied responses (good for sales, engaging conversations)

First Sentence

Set the opening line to control how the call starts:
The first sentence is critical. It sets the tone and immediately establishes context. Make it clear, friendly, and specific.

Best Practices

Do This

  • Be specific: Include exact scenarios and how to handle them
  • Set boundaries: Define what the AI should and shouldn’t do
  • Use variables: Use {{variable}} syntax for personalization
  • Test thoroughly: Try different scenarios before going live
  • Iterate: Refine instructions based on real call transcripts

Avoid This

  • Vague instructions: “Be helpful” is too generic
  • Conflicting goals: Don’t ask the AI to both sell and not be pushy without clear boundaries
  • Missing context: Provide relevant information about the customer or situation
  • Too long: Keep instructions focused, around 200-500 words

Next Steps

Voice Library

Browse available voices and learn about voice cloning.

Function Calling

Give your AI tools to interact with your systems mid-call.