Designing a World for an AI Narrator Starts Small
Designing a world for an AI narrator is mostly subtraction: fix the few facts a scene can be checked against, and leave the rest for the story to invent.
Designing a world for an AI narrator is mostly a subtraction problem. Every fact you fix in advance has to be carried into the prompt on every turn, where it competes for attention with the scene at hand; every fact you leave open is room the story can fill while you read. The file that works is short, specific, and honest about its own gaps.
- A world file for a live narrator is prompt material, not reference material: it is read again on every single turn.
- Anthropic’s prompting guidance tells developers to “Put longform data at the top” of a prompt, above the query and instructions.
- A machine-checkable world is a specification with countable parts: TextWorld generates games from options like
--world-sizeand--nb-objects.- A fact invented during a story binds the next scene as tightly as one written before the story started, once it is recorded.
- Run the same opening three times: where the runs agree you never needed a fact, and where they disagree you do.
Why designing a world for an AI narrator is a subtraction problem
Because the world file is not filed anywhere. It is pasted into the prompt for scene one, scene two and scene ninety, alongside the story’s memory and the move you just wrote. A reference book costs nothing to own and something to open; a world file costs something every time the narrator writes a sentence, which is always.
That cost is not only money. Position and structure change what a model does with what it is given. Anthropic’s prompting best practices for Claude tell developers to “Put longform data at the top” of a prompt, “above your query, instructions, and examples,” and note that queries placed at the end “can improve response quality by up to 30 percent in tests.” Arrangement is part of the design, not a detail of plumbing.
So the question for every candidate fact is not whether it is interesting. It is whether it earns a place in the material the narrator re-reads before it writes the next paragraph. Most lore does not. Three sentences about the guild’s founding will be present at the moment you are trying to climb a wall, and their only effect will be a slightly less attentive wall.
What actually belongs in the file
Four kinds of fact, and not much else. Each of them shares a property: a scene that contradicts it is broken rather than surprising. That is the test for inclusion, and it excludes nearly everything a worldbuilder enjoys writing.
| Kind of fact | Example | What breaks without it |
|---|---|---|
| Recurring proper nouns | The Emberwood; Ironreach Station | A place or person renamed halfway through |
| Physical constants | Four hundred crew, and they are gone | Distances and deadlines a reader planned around |
| The standing pressure | Something already going wrong before you arrive | Scenes with nowhere to point, so they describe |
| The declared content level | An age rating stated on the cover | A reader ambushed by a register they did not choose |
Everything in that table is checkable. A later scene either agrees with it or does not, and you can tell which by reading. Compare that with “the forest is ancient and watchful,” which no sentence can contradict, and which therefore does no work beyond tinting the prose. The longer argument for constraint over atmosphere is what a world has to be able to refuse.
What we leave out on purpose
The map past walking distance. The history before the pressure. Numbers nobody will ever count. The names of people you have not met. And, deliberately, the answer to the question the world is built around — written down nowhere, so that no scene can leak it early.
Leaving these out is not laziness about the parts we have not imagined. It is a claim about how fixed detail behaves once it is in the prompt:
- Stated mood comes back as stated mood. A file that says the corridors feel abandoned will get abandoned corridors described to you in scene after scene. That is one of the quieter roads into stories that repeat themselves.
- Unfilled space gets filled specifically. Asked for a stranger’s name, a narrator produces one, in context, with a face attached. Asked to reuse a name from a roster of forty, it produces the roster.
- A gap reads as depth. A world that declines to explain itself is doing what novels do. A world that explains itself upfront has spent the thing it could have withheld.
The working rule: write the fact when the story first needs it, not when you first think of it. An invented detail is not a problem. An unrecorded one is.
How do you find the facts you forgot to write?
Run the same opening three times and read the three side by side. Wherever the narrator invented the same thing in all three runs, the world file was already constraining it and you never needed a line. Wherever the three disagree, you have found a gap, and the disagreement tells you exactly which sentence to write.
Three runs is enough to be useful and cheap enough to do before breakfast. Five is better if the world is strange. The method has a second benefit: it shows you what your file is accidentally forcing. A detail that comes back identically in every run, and that you never wrote, is being implied by something you did write — worth knowing before it hardens.
Why a coded world does not need this test
Because it cannot have the problem. In a world built as a program, the parts are enumerated before anyone plays. Microsoft’s TextWorld, described as “a text-based game generator and extensible sandbox learning environment,” builds its games from options that count things: --world-size for rooms, --nb-objects for interactive objects, --quest-length for the commands needed to win. Nothing in such a world is undefined, and nothing in it can be invented mid-scene either. That is the trade.
The world keeps being written while you read
After the first scene the file has stopped being the world. The record has become the world: what was said, who was met, which promise was made and to whom. A fact invented in scene four is binding in scene forty, which is the whole reason an AI story can hold together at all, and the reason authored facts are only the seed.
Fabledrift, an interactive fiction app for Android, hands the narrator a structured record of facts, characters, places and promises on every turn, and that record grows as you read. Readers can add their own notes to it, and when a note contradicts the story record, the note wins. So the world file is a first draft that the reading finishes — which is why we would rather start it thin.
What we would cut from our own world files first
Most of designing a world for an AI narrator turns out to be deciding what not to fix, and the cuts go in a fixed order. The history. Then the adjectives. Then any number nobody in the story will be asked to count. What survives that cut in the two worlds we ship is small enough to say aloud: the Emberwood remembers every promise made beneath its branches, and Ironreach Station should have a crew of four hundred who are not there. Both are rules before they are settings, and both leave more unsaid than said.
Take a world you already like and cut it to four facts of that kind. Then run the opening three times and see what you actually miss.
Frequently asked questions
How long should a world file for an AI narrator be?
Short enough that you would be willing to re-read it before every scene, because the narrator does. One page of load-bearing facts travels further than twenty pages of history, and the rest can be written as the reader reaches it.
Does a bigger world file make a better story?
No. Past a point it makes a flatter one. Fixed detail arrives in every scene whether or not the scene needs it, so an over-specified world tends to hand back its own adjectives instead of answering what you just did.
What should never be left out of a world file?
The proper nouns that will recur, the physical constants a reader can plan against, the pressure already underway, and the declared content level. Those four are the ones a story cannot quietly reinvent without breaking.
How do you find the facts you forgot to write?
Run the same opening scene three times and compare what the narrator invented. Details that come back the same were never worth writing down; details that come back differently are the gaps in your world file.
Do facts invented mid-story count as part of the world?
Yes, once they are recorded. A name the narrator gives a stranger in scene four binds scene forty exactly as tightly as anything you wrote in advance, provided it goes into the story's record rather than staying in the prose.