How to create an AI character with a voice of their own

Start with a playable premise

To create an AI character, define who they are, what they want, how they speak and why the conversation starts now. Then write a greeting that gives the other person something to respond to. A vivid premise usually does more work than a long list of adjectives.

“A mysterious detective” is a label. “A former investigator has invited you to a café because a photograph shows an evening you do not remember” is a situation you can play. There is a question, a relationship and a reason for the next message.

In Koimo, open your library and choose to create a character. Use the name, description, personality, scenario, greeting and example-dialogue fields to build the premise. You can also import an existing character card instead of starting from a blank sheet.

Write a small, coherent character sheet

Here is an original example you can adapt. Mara is an adult fictional character, separate from Koimo’s original cast.

Name: Mara
Tagline: The lighthouse stays lit.

Description: An adult lighthouse keeper on a working island.
She knows every boat by its engine and keeps letters she never sends.

Personality: Practical and dryly funny. She offers help through
small actions. When a question gets personal, her answers get shorter.
She wants someone to stay, but refuses to ask them to.

Scenario: A storm has stopped the last ferry. A visitor arrives
at the lighthouse with a broken radio and an unopened letter.

Greeting: Mara opens the door before you knock a second time.
"Ferry's gone. If that's a radio, bring it in. If it's bad news,
at least shut the door before you tell me."

Example dialogue:
You: Do you get lonely out here?
Mara: The gulls are terrible company. Tea?
You: That wasn't an answer.
Mara: It was an invitation. I'm told they're different.

Notice that the personality describes choices and habits. It does not demand a catchphrase in every message or require a fixed gesture whenever she is nervous. The dialogue demonstrates an indirect answer without explaining the joke.

Keep facts consistent across fields. If the scenario says the ferry has left, the greeting should not put the visitor on that ferry. Remove decorative details that never affect behavior before adding more lore.

Teach voice through examples

Write a few short exchanges for different situations: a greeting, a disagreement, an honest compliment and a personal question. Show how the character responds when comfortable and when under pressure. Range is more useful than ten examples of the same joke.

A useful direction is “Mara answers personal questions indirectly until she trusts someone.” A brittle direction is “Mara must always mention the sea, adjust her coat and call the user sailor.” The second can turn every reply into the same performance.

Leave the player’s words and choices to the player. The character can offer tea, warn about the storm or ask for the letter. They should not decide that the player accepts, becomes frightened or falls in love.

Test before adding more detail

1. Send a plain greeting. Does the reply sound like this character without forcing the entire backstory into it?
2. Disagree with them. Do their motives shape the answer, or do they agree with anything?
3. Ask a personal question. Does the shift in voice fit the personality?
4. Change the pace. Try one short reply and one longer action. Check that the character gives you room to act.
5. Correct a mistake. State the correction clearly. If the same error returns, revise the conflicting sheet detail.

Koimo’s character editor includes a draft Test chat for trying the sheet. Change one part, test again, and keep the version that plays better. No definition guarantees perfect behavior from a language model.

Keep an export of work you want to preserve. Koimo supports character-card exports in V2/V3 formats; importing into a different app can change behavior because the model and prompt setup may differ. Our memory guide explains why a character definition and a story’s evolving continuity belong in different places.

Ready to write? Open the character editor, or meet the original cast for examples of different premises.

Keep writing.

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