How to Write AI Character Cards: A Practical Starter Guide

A character card is a structured prompt that tells an AI who to portray and how the story should work. This guide completes my introductory series on lorebooks and fictional inner thoughts. Reading stories and paying attention to characterization will help more than collecting a long list of prompt tricks.

Start with five basic sections

Describe the setting, character identity, world, rules, and interaction with the player. My examples use a single main character, but you can extend the same structure to multiple characters. Different writers organize cards differently; the important thing is that the instructions are clear and consistent.

Character identity
Relationship / affinity rules
Narration style
Dialogue format
Opening scene

Modern-setting cards

Give the character a name, personality, age, and background. If you track affinity, specify its initial value, how it rises or falls, and what changes at particular thresholds. For example:

When affinity exceeds 30, the character becomes more comfortable interacting with {User} and begins initiating conversations.

Explain the narration style: perhaps scene descriptions use parentheses while spoken dialogue uses quotation marks. If you want a visible relationship meter, define the output format:

Line 1: Affinity: {affinity} {change}
Line 2 onward: Character dialogue and scene narration

An opening scene gives the user something to respond to. Examples can also demonstrate the desired voice, although you do not need them for every card:

Scene: It is a sunny weekend morning. {User} is still in their room. The character has just woken up in oversized bear pajamas, with tousled hair, and knocks on the door while holding a plush toy.

Fan-made character cards

Revisit the original work before writing. Record the character's background, speech patterns, and relationships. A few short dialogue examples can help demonstrate the voice; use your own examples or material you have permission to reproduce. A lorebook can hold extra setting information without keeping everything permanently in the main prompt.

The fictional inner-thoughts tutorial (Chinese original) shows another way to enrich the presentation. For the opening, think about how the character and player first meet and what makes that encounter believable.

Historical or game-style cards

For a game such as running an old-fashioned restaurant, add attributes, places, activities, and an economic system. Define what each turn changes instead of leaving the model to invent every calculation.

Starting attributes: strength, intelligence, and charisma.
The player may choose values or use a defined random allocation.
Training locations improve specific attributes.
Thresholds unlock events: intelligence 60 enables one route; charisma 50 changes a relationship outcome.

Plan enough locations to give the story variety, explaining what can happen in each, who may appear, and which resources are spent. For complex games, use a lorebook and a memory mechanism, and check state calculations regularly: models can still lose settings or mix up numbers.

My original Chinese cards often used roughly 2,000–3,000 characters for modern or fan settings and 3,000–5,000 for larger game setups. Those are examples, not required lengths. More text is not always better; remove contradictions and unnecessary repetition. The five basic sections above provide a useful starting point, then testing shows where the card needs improvement.

Adapted from the original Chinese article, published on May 25, 2026.