OnlyWorlds docs

An open standard for worldbuilding data, and the API, SDKs and agent interfaces to build on it.

Build an appThe TypeScript, Python and Unity SDKs, or plain REST.

Connect an agentThe MCP server, agent seats, the LLM guide and the toolkit.

Understand the schemaThe 22 element types, their fields and typed links.

Build a world without codeStart at onlyworlds.com/start, or open Atlas: a world as plain files on your own disk, no account needed.

Pick a toolAtlas, Lantern, the Obsidian plugin and the others, what each does, and how to bring in your notes.

Admiral Fluffington of the demo world Moppetopia, shown as the standard’s YAML, the API’s JSON, an AI assistant’s answer, Atlas and the Unity World Browser.

One element, in the places it lives. Admiral Fluffington is in the public demo world Moppetopia; the worked example walks the same calls.

Quickstart

List the Characters in Hyperion, the public example world. Its demo key 0000000000 is read-only and reads without a PIN. Moppetopia, the world most of these docs use, reads the same way with 0000000001 (demo keys).

curl -H "API-Key: 0000000000" \

  "https://www.onlyworlds.com/api/v2/character/?fields=id,name"

{

  "data": [

    { "id": "068e92dc-10ec-7225-8000-7efd678bd862", "name": "Mr. Steinway" },

    { "id": "068e92db-4c40-79eb-8000-8ef44c0d52b4", "name": "Rachmaninov" },

    { "id": "068e2ddb-83c6-71a7-8000-a45b8b711e25", "name": "The Consul" }

  ],

  "has_more": false,

  "next_cursor": null

}

Swap in a key for your own world and the same call reads it. To try a write without an account, use the practice world, a copy of Moppetopia anyone may write to. Your first hour does a read, a write and a delete in TypeScript, Python or curl in a few minutes, and Getting started walks through keys.

Looking for tools to build a world with, rather than to build on? Start at onlyworlds.com/start, open Atlas, or read the Tools page.