Build a Persona for Your Avatar

How to write a system prompt, greeting, and LLM config for an AI avatar persona on ACE AI Spark. Includes a 45-second walkthrough video.

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An avatar is a face. A persona is the personality, knowledge, and voice that face uses to talk. You can give one avatar several personas — a friendly receptionist persona on your homepage, a technical-support persona on your help page — and switch between them.

Watch the 45-second walkthrough

Quick Summary: Open AI Avatars → Personas tab → New Persona → name + linked avatar + system prompt + greeting + language/LLM → Create.

Step-by-Step Walkthrough

Open the Personas tab

On the AI Avatars page, click the Personas tab. You will see any personas you have already created.

Click New Persona

Opens the persona builder dialog.

Give it a name

This is the persona display name — viewers will not see it but you will (in the dropdowns when picking which persona an embed uses).

Link an avatar

Pick which AI avatar this persona will use as its face. If you have not built one yet, head back to Create Your First AI Avatar.

Write the system prompt

This is the persona personality and role — what it knows, how it talks, what it should never say. Be specific:

Who is the persona? ("You are Agent Luna, the AI receptionist for ACME Software.")
What can it help with? ("You help users understand our pricing, book demos, and answer feature questions.")
Tone? ("Friendly, concise, never pushy.")
What should it avoid? ("Never make promises about delivery dates.")

The prompt is read aloud by the LLM behind the avatar, so write it conversationally — no markdown, no bullet lists. Plain sentences work best.

Set the opening greeting

The first thing your avatar says when a viewer joins the call. Make it warm and specific to the avatar role: "Hi! I am Luna — what can I help you with today?"

Pick language and LLM

The defaults (English, and the fast standard model) work well for most use cases — quick to respond and inexpensive to run. Switch to a heavier model only if you need more reasoning depth — at the cost of slightly higher latency.

Click Create Persona

The persona is active immediately. It will appear in the Personas tab as a card, ready to be used by the embed widget or share link.

Writing a Good System Prompt

Be the persona, not about the persona — write "You help users…" not "This persona helps users…". The LLM speaks in second person.
Cover the negative space — explicitly tell it what NOT to say. ("Never quote prices that are not on our pricing page.")
Keep it under 400 words — longer prompts increase response latency. Trim aggressively.
Test it live — start a conversation with the persona before sharing it externally. You will catch tone issues fast.

What is Next

Now that your persona is built, you are ready to put it in front of visitors. Learn how to share a link or embed the widget on your website.