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Writing Instructions

The instructions decide who the agent is, what it’s after and how it behaves. Good instructions cover five things.

1. Identity & Role

2. Goal & Context

3. Tone & Style

4. Handling Scenarios

5. Boundaries

Instructions alone can’t move a caller to a person. For that, set up a transfer.

Complete Example

Model Selection

Live

One voice model hears and speaks. A second model runs the agent’s actions, like calling your tools or handing off between crew members, and model picks it from live.llm in GET /v1/models (anything else returns 400). Left out, the call uses the entry marked default: true. Send mode: "live" with it, since a model without a mode runs Legacy.

Legacy

model picks the model that writes every reply, from legacy.llm in GET /v1/models.

Voice Selection

Live Voices

live_voice takes one of 13 voices: marin, quartz, ripple, vesper, willow, stone, gleam, meridian, bossa, tempo, beacon, delta, cinder. Leave it out and the call picks one for its language.

Legacy Voices

About 50 built-in voices, male and female. Pass a voice ID from GET /v1/voices/builtin or GET /v1/voices as voice.

Language & Dialect Control

Live

  • stt_language (or stt_languages for several) sets the starting language and the default live voice. Use a code from supported_languages in GET /v1/models; anything else returns 400
  • The agent switches language only when your instructions allow it

Legacy

  • stt_language (or stt_languages) sets the speech recognition language, dialect included: en-GB vs en-US
  • The agent speaks only those languages. Instructions can’t add another
  • Up to 78 languages. The exact set depends on the speech recognition and voice models

Temperature

temperature runs from 0 to 1 and defaults to 0.7. Lower is steadier, which suits confirmations. Higher varies more, which can suit sales.
A model whose supports_temperature is false in GET /v1/models ignores it.

First Sentence

The opening line, spoken when the call connects. Legacy says it word for word; Live may reword it slightly.
Keep it short and say who’s calling and why in the first breath.

Best Practices

  • Name the scenarios and what to do in each. “Be helpful” tells the model nothing.
  • Say what the agent must never do.
  • Personalize with {{variable}} placeholders.
  • If you want “sell, but don’t push”, say where the line is.
  • Aim for 200 to 500 words.
  • Test on a few calls and rewrite from the real transcripts before you scale.

Next Steps

Voice Library

Browse the built-in voices for each mode.

Function Calling

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