How to write a character card

A character card is the description a model reads before it says anything. Most characters that feel flat are not badly written — they are over-written. This guide covers each field on Stella and what actually earns its place there.

Name and presentation name

The name is what the model is told it is called. The presentation name is what visitors see in the catalogue. Keep them the same unless you need a display title — “Captain Ada Reyes” on the card, “Ada” to the model — and avoid stuffing keywords into either; it reads as spam to browsers and to search engines alike.

Description

The description does double duty: it is the pitch a visitor reads before deciding to chat, and it is indexed by search engines. Write the first two sentences for a person who has never heard of the character. Say who they are, where they are, and what a conversation with them is like. Save the biography for later paragraphs.

Aim for 100–400 words. Concrete details beat adjectives: “keeps a tally of every favour owed” tells a model more than “cunning and calculating”.

Greeting

The greeting is the character’s first message, and it sets the format for everything after it. If you open with three paragraphs of scene-setting prose, replies will be three paragraphs of prose. If you open with one line of dialogue, replies stay short. Put the user somewhere specific — a place, a moment, an unanswered question — rather than a neutral “Hello, how can I help?”.

Alternate greetings let one character open in several different situations. Use them for genuinely different starting scenes, not minor rewordings.

System prompt

The system prompt is instruction, not description. It belongs to rules the model must follow regardless of what is being discussed: point of view, tense, response length, what the character will never do, whether narration is allowed. Write it as directives — “Reply in second person, present tense. Never break character to explain yourself.” Repeating the description here wastes context.

Personality

A short list of traits, speech habits, and pressure points. The useful entries are the ones that change how a sentence comes out: a verbal tic, a subject they deflect, a register they drop into when angry. Five sharp traits outperform twenty generic ones.

Example dialogue

Example exchanges are the strongest lever you have over voice, because the model imitates them directly. Two or three short exchanges are usually enough. Choose ones that demonstrate something the description cannot state — rhythm, humour, how the character refuses — and write them at the length you want replies to be.

Avatar

Upload a square image; it is re-encoded to WebP and displayed as the card and page portrait. A clear subject at small sizes matters more than resolution, since most visitors first see it as a thumbnail in the grid.

Test before you publish

Start a chat with your own character and push at it: ask something off-topic, ask it to break character, let a scene run for ten messages. Most fixes belong in the system prompt or the examples, not in a longer description.

Next: what makes an AI character compelling, or what a lorebook is and when to use one.