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OnlyWorlds

REMOTE · WWW.ONLYWORLDS.COM · SCANNED SEP 27

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

0 this week 73 Trust /100
Trust breakdown (7 categories)

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →

Endpoint Security57
Transport & Reachability100
Schema Quality & AI Usability59
  • AI-judged instruction clarity (good).Pass
  • Context-footprint check failed: tool/resource definitions use about 2017 tokens (~183/item across 11 items; 11 tools + 0 resources), over budget; trim descriptions and params. See how to fix → Fail
  • Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management100
  • No destabilizing schema changes in the last 30 days.Pass
Tool Coverage71
  • 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
  • 0% of tool parameters carry a description.Fail
  • Structured output schemas are declared (100% of tools); any adoption earns full credit.Pass
Tool Safety100
  • No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
  • We read all 11 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
  • An AI judge read all 11 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
  • Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.Pass
Install

How do I install the OnlyWorlds MCP server?

OnlyWorlds is a hosted endpoint at https://www.onlyworlds.com/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

remote · www.onlyworlds.com

# add to Claude Code
claude mcp add --transport http com-onlyworlds-mcp 'https://www.onlyworlds.com/mcp'
// .cursor/mcp.json
{
  "mcpServers": {
    "com-onlyworlds-mcp": {
      "url": "https://www.onlyworlds.com/mcp"
    }
  }
}
// .vscode/mcp.json
{
  "servers": {
    "com-onlyworlds-mcp": {
      "type": "http",
      "url": "https://www.onlyworlds.com/mcp"
    }
  }
}
# ~/.codex/config.toml
[mcp_servers.com-onlyworlds-mcp]
url = "https://www.onlyworlds.com/mcp"
// opencode.json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "com-onlyworlds-mcp": {
      "type": "remote",
      "url": "https://www.onlyworlds.com/mcp",
      "enabled": true
    }
  }
}
# add to OpenClaw
openclaw mcp add com-onlyworlds-mcp --url 'https://www.onlyworlds.com/mcp' --transport streamable-http
# ~/.hermes/config.yaml
mcp_servers:
  com-onlyworlds-mcp:
    url: "https://www.onlyworlds.com/mcp"
// ~/.netclaw/config/netclaw.json
{
  "McpServers": {
    "com-onlyworlds-mcp": {
      "Transport": "http",
      "Url": "https://www.onlyworlds.com/mcp"
    }
  }
}
# add to Vellum
assistant mcp add com-onlyworlds-mcp -t streamable-http -u 'https://www.onlyworlds.com/mcp'
// mcp.json
{
  "mcpServers": {
    "com-onlyworlds-mcp": {
      "type": "http",
      "url": "https://www.onlyworlds.com/mcp"
    }
  }
}

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

Changelog

Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.

  • 25 Sept 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 26 Aug 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 25 Aug 26 0
    • Stability: 0.97 → pass security
  • 11 Aug 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 7 Aug 26 0
    • The server no longer declares the “experimental” capability functional
  • 31 Jul 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 30 Jul 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 27 Jul 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
Diagnostics

Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.

Captured 27 Sept 2026 · Probed https://www.onlyworlds.com/mcp

TLS valid

Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .

Subject Issuer Valid from Valid until Key Signature Serial
CN=www.onlyworlds.com CN=WE1,O=Google Trust Services,C=US 8 Sept 2026 7 Dec 2026 ECDSA 256 ECDSA-SHA256 38b3181b4ad127c913d3a4295ecb368e
SANs: www.onlyworlds.com
CN=WE1,O=Google Trust Services,C=US (CA) CN=GTS Root R4,O=Google Trust Services LLC,C=US 13 Dec 2023 20 Feb 2029 ECDSA 256 ECDSA-SHA384 7ff31977972c224a76155d13b6d685e3
CN=GTS Root R4,O=Google Trust Services LLC,C=US (CA) CN=GlobalSign Root CA,OU=Root CA,O=GlobalSign nv-sa,C=BE 15 Nov 2023 28 Jan 2028 ECDSA 384 SHA256-RSA 7fe530bf331343bedd821610493d8a1b

Background: What to check on a remote MCP endpoint →

DNSSEC insecure

Validation of www.onlyworlds.com. — Not signed

Zone DS Keys Algorithms Outcome
. trust_anchor 20326, 38696 8, 8 Verified
com. present 19718 13 Verified
onlyworlds.com. absent Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation
Authentication No authorisation required

The endpoint answered without asking for a token. Anyone who knows the URL can reach it.

Result No authorisation required
HTTP status 200

Background: How OAuth 2.1 works in the 2026 MCP spec →

Transports 2 probes
Transport URL Outcome Status Location
streamable-http https://www.onlyworlds.com/mcp Verified 200
http (plaintext) http://www.onlyworlds.com/mcp HTTPS enforced 301 https://www.onlyworlds.com/mcp
MCP tools · 11 exposed · ~2,017 tokens

The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →

Tool Tokens
bulk_apply ~254

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).

NameTypeReqDescription
atomicboolean––
itemsarrayyes–

Structured output declared, but exposes no named fields.

No examples provided.

create_element ~201

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.

NameTypeReqDescription
elementobjectyes–
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

edit_links ~258

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.

NameTypeReqDescription
add–––
fieldstringyes–
idstringyes–
remove–––
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

get_changes ~244

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`.

NameTypeReqDescription
limitinteger––
since_cursor–––

Structured output declared, but exposes no named fields.

No examples provided.

get_element ~134

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.

NameTypeReqDescription
idstringyes–
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

get_element_schema ~154

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.

NameTypeReqDescription
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

list_element_types ~109

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.

Input schema present but exposes no named parameters.

Structured output declared, but exposes no named fields.

No examples provided.

list_elements ~180

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.

NameTypeReqDescription
limitinteger––
name_contains–––
offsetinteger––
supertype–––
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

search_elements ~120

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.

NameTypeReqDescription
querystringyes–

Structured output declared, but exposes no named fields.

No examples provided.

search_schema ~115

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.

NameTypeReqDescription
querystringyes–

Structured output declared, but exposes no named fields.

No examples provided.

update_element ~248

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.

NameTypeReqDescription
fieldsobjectyes–
idstringyes–
typestringyes–

Structured output declared, but exposes no named fields.

No examples provided.

Common questions

What is the OnlyWorlds MCP server?

OnlyWorlds is an MCP server listed in the public MCP registry as com.onlyworlds/mcp. Read and write typed fictional worlds (22 linked element types) via the OnlyWorlds open standard. This page covers its hosted endpoint (https://www.onlyworlds.com/mcp).

Is the OnlyWorlds MCP server safe to use?

OnlyWorlds scores 73 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

What tools does the OnlyWorlds MCP server expose?

OnlyWorlds exposes 11 tools: list_element_types, get_element_schema, search_schema, list_elements, get_element, and 6 more. Their descriptions and schemas cost roughly 2,017 tokens of context every time the server is loaded.

Does the OnlyWorlds MCP server require authentication?

No. We connected to OnlyWorlds without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

Is the OnlyWorlds MCP server still maintained?

OnlyWorlds is still listed as active in the MCP registry. We last reached this channel on 27 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.