# OnlyWorlds MCP server

Read and write typed fictional worlds (22 linked element types) via the OnlyWorlds open standard.

## Links
- Registry page: https://www.getdrio.com/mcp/com-onlyworlds-mcp
- Website: https://www.onlyworlds.com

## Install
- Endpoint: https://www.onlyworlds.com/mcp
- Auth: Auth required by registry metadata

## Setup notes
- Remote header: API-Key (required; secret)
- Remote header: API-Pin (secret)
- The upstream registry signals required auth or secrets.
- Remote endpoint: https://www.onlyworlds.com/mcp
- Header: API-Key
- Header: API-Pin

## Tools
- list_element_types - List all 22 OnlyWorlds element types with a one-line shape summary of each.

Every world is built from these types; each element has a stable UUID `id`, a
`name`, and a `type`. Use `get_element_schema(type)` for a type's full field
list. Unauthenticated — schema is public reference. Returns a mapping of the 22
type slugs (the value you pass as `type` to the data tools) to a summary
string. Endpoint: https://www.onlyworlds.com/mcp
- get_element_schema - Return the field structure of one OnlyWorlds element `type` (a slug from
`list_element_types`, e.g. "character").

The result groups the type's writable fields by kind so a caller knows how to
read and write them: `text` (strings), `integer`, `single_link` (one UUID),
`multi_link` (an array of UUIDs), and `generic` (a type+id pair pointing at any
element type). For every link field the target element type is given under
`link_targets`. All link values are element UUIDs. Unauthenticated. Errors if
`type` is not one of the 22 types. Endpoint: https://www.onlyworlds.com/mcp
- search_schema - Search every element type's fields for `query` (case-insensitive substring),
across all 22 types. Useful for "which types have a `location` field?" or
finding where a concept lives in the schema.

Returns a mapping of type slug -> the matching field names in that type (types
with no match are omitted); a `query` that also matches a type slug lists that
type with an empty field list so the type-name hit is not lost. Unauthenticated. Endpoint: https://www.onlyworlds.com/mcp
- list_elements - List elements of one `type` in the world named by your API-Key header,
newest-created first.

`type` is a slug from `list_element_types` (e.g. "character"). Optional
`name_contains` filters by case-insensitive name substring; `supertype`
filters exactly. `limit` (default 100, max 1000) and `offset` page the result.
Requires a READ or WRITE API-Key. Returns `{data: [element, ...], limit,
offset, has_more}` where each element is the full v2 wire shape and `id` is a
UUID. Use `get_element(type, id)` for a single element. Endpoint: https://www.onlyworlds.com/mcp
- get_element - Fetch one element by `type` and `id` (a UUID) from the world named by your
API-Key header.

`type` is a slug from `list_element_types`. Returns the full v2 wire shape
(the same body as `GET /api/v2/{type}/{id}`): `type`, `id`, `name`, scalar
fields, link fields as UUID arrays, and any extension fields inline. Requires a
READ or WRITE API-Key. Errors if no element of that type with that id exists in
the world. Endpoint: https://www.onlyworlds.com/mcp
- search_elements - Search elements by name across ALL 22 types in the world named by your
API-Key header (case-insensitive substring match).

Use this when you know part of a name but not the element's type. Bounded to at
most 50 matches per type. Returns `{query, results: [{type, id, name,
supertype, subtype}, ...]}` — `id` is a UUID; call `get_element(type, id)` for
the full body. Requires a READ or WRITE API-Key. Endpoint: https://www.onlyworlds.com/mcp
- get_changes - Return the delta feed for the world named by your API-Key header: every
element created/updated (`op: "upsert"`, full body) or deleted (`op:
"delete"`) since `since_cursor`, in apply order, in pages of `limit`
(default 25, max 1000). Entries carry FULL element bodies — a default page
stays inside any client's token budget; measured worlds ran ~1.5-2k chars
PER ENTRY, so raise `limit` only if you truly need bigger pages, and prefer
paging with the cursor.

Omit `since_cursor` (or pass "") to start from the beginning of the feed —
for a big world that is a multi-page walk, not one response. Pass the
returned `cursor` back as `since_cursor` to get the next page (or, later,
only what changed since); treat the cursor as OPAQUE. `has_more` true means
page again with the new cursor. Requires a READ or WRITE API-Key. This
mirrors `GET /api/v2/changes`. Endpoint: https://www.onlyworlds.com/mcp
- create_element - Create one new element of `type` in the world named by your API-Key header.

`type` is a slug from `list_element_types` (e.g. "character"). `element` is the
field payload: `name` plus any scalar, link, or extension fields for that type
(call `get_element_schema(type)` for the field structure). Link fields are UUID
arrays (multi) or a single UUID (single); every linked id must already exist in
the world. Supply your own `id` (a UUID) to mint the element at that id, or omit
`id` and the server mints a uuid7. Requires a WRITE API-Key. Returns the full
created element in the v2 wire shape. Errors (naming the offending field) on an
unknown field, a bad link target, or an id that already exists. Endpoint: https://www.onlyworlds.com/mcp
- update_element - Update an existing element by `type` and `id`, changing ONLY the fields you
pass — omitted fields are preserved.

This is a server-side read-merge: the current element is loaded and only the
keys in `fields` are applied, so it is safe against the raw-HTTP-PATCH hazard
where sending a partial link array replaces the whole array. Semantics per field
kind: a text field you pass is set (pass an empty string `""` to clear it); a
multi-link field you pass REPLACES that field's array wholesale (pass an empty
array `[]` to clear it) — for additive/subtractive link edits that leave the
rest of the array intact, use `edit_links` instead. `type` is a slug from
`list_element_types`; `id` is the element's UUID. Requires a WRITE API-Key.
Returns the full updated element in the v2 wire shape. Errors if the element
does not exist, or (naming the field) on an unknown field or a bad link target. Endpoint: https://www.onlyworlds.com/mcp
- edit_links - Add and/or remove links on ONE multi-link `field` of an element, leaving the
rest of that field's array untouched.

Use this for additive/subtractive link edits (unlike `update_element`, which
REPLACES a link array). `type` is a slug from `list_element_types`; `id` is the
element's UUID; `field` must be a multi-link field on that type (see
`get_element_schema(type)`). `add` is a list of UUIDs to link (each must already
exist in the world; adding an already-linked id is a no-op) and `remove` is a
list of UUIDs to unlink (removing an absent id is tolerated). Requires a WRITE
API-Key. Returns `{type, id, field, values}` where `values` is the field's full
UUID array after the edit. Errors (naming `field`) if it is not a multi-link
field of this type, if the element does not exist, or if an added target id is
absent. Endpoint: https://www.onlyworlds.com/mcp
- bulk_apply - Create and/or update many elements across any of the 22 types in one call.

Each entry in `items` is `{"type": <slug>, "element": <payload>}` with the same
payload shape `create_element` takes: an `element` with an `id` UPDATES that id
(creating it if absent), an `element` without an `id` CREATES a new element.
Items may reference each other by id, including a forward reference to a sibling
later in the list. There is NO delete: bulk_apply never removes an element.
When `atomic` is false (default), items succeed or fail independently and the
response reports each outcome; when `atomic` is true, ANY item failure rolls the
whole batch back and nothing is committed. Up to 1000 items. Requires a WRITE
API-Key. Returns the batch response verbatim: `{errors, items: [{status, id,
created_at, updated_at} | {status, id, error}, ...]}` — `errors` true means at
least one item failed (and, under `atomic`, that nothing committed). Endpoint: https://www.onlyworlds.com/mcp

## Resources
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## Prompts
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## Metadata
- Owner: com.onlyworlds
- Version: 1.0.0
- Runtime: Streamable Http
- Transports: HTTP
- License: Not captured
- Language: Not captured
- Stars: Not captured
- Updated: Jul 24, 2026
- Source: https://registry.modelcontextprotocol.io