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 categories, 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.

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’s demo key is listed on Keys and PINs.

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. Getting Started walks through keys and the first write.

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