Castle MCP by usefulapi

by usefulapi.io · remote · no sign-in to list tools · v1.16.3 · published by io.usefulapi

Investigate security events and manage the allow/deny lists an analyst acts on.

Deletes · 6Changes · 1

Compare Registry entry

14 tools: 6 can delete or cancel things, 1 change things and 7 only read.

Scanned Oct 21, 2026

Deletes or cancels6Claude Code: deny: see these tools
Can't be undone0Claude Code: ask
Changes things1Claude Code: ask: see these tools
Only reads7Claude Code: allow: see these tools

1 check matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http castle https://castle.usefulapi.io/mcp

Findings

Matches of fixed checks, with the text they matched.

1 warn

Warncastle_unarchive_list_item
The server marks "castle_unarchive_list_item" destructive (destructiveHint: true), and its name says "list", a word for reading.
Matched text
annotations: {"destructiveHint":true}; The name "castle_unarchive_list_item" says "list": a word for reading.
What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

14 tools

Deletes or cancels 6Removes, cancels or revokes something.Claude Code: deny

castle_archive_list_itemArchive a list entry so it stops matching.No findings
Why it is in this group
- The name "castle_archive_list_item" says "archive": a word for removing or ending something.
- The server marks it destructive (destructiveHint: true).
Description, as the server wrote it
Archive a list entry so it stops matching. Reversible with castle_unarchive_list_item. Castle: DELETE /v1/lists/{list_id}/items/{id}/archive.
Annotations the server declares
- title: Archive a list item
- destructiveHint: true
castle_create_listCreate a new allow or deny list.No findings
Why it is in this group
- The name "castle_create_list" says "create": a word for a change.
- The server marks it destructive (destructiveHint: true).
Description, as the server wrote it
Create a new allow or deny list. primary_field is the event field its entries match on, e.g. ip or user.email. Castle: POST /v1/lists.
Annotations the server declares
- title: Create a list
- destructiveHint: true
castle_create_list_itemAdd an entry to a list — for example block an IP or an email.No findings
Why it is in this group
- The name "castle_create_list_item" says "create": a word for a change.
- The server marks it destructive (destructiveHint: true).
Description, as the server wrote it
Add an entry to a list — for example block an IP or an email. This changes live policy behaviour. Castle: POST /v1/lists/{list_id}/items.
Annotations the server declares
- title: Add an item to a list
- destructiveHint: true
castle_unarchive_list_itemRestore a previously archived list entry so it matches again.1 finding
Why it is in this group
- The name "castle_unarchive_list_item" says "list": a word for reading.
- The server marks it destructive (destructiveHint: true).
Findings
- Warn
  The server marks "castle_unarchive_list_item" destructive (destructiveHint: true), and its name says "list", a word for reading.
  Matched text
  annotations: {"destructiveHint":true}; The name "castle_unarchive_list_item" says "list": a word for reading.
  What this check looks for
Description, as the server wrote it
Restore a previously archived list entry so it matches again. Castle: PUT /v1/lists/{list_id}/items/{id}/unarchive.
Annotations the server declares
- title: Unarchive a list item
- destructiveHint: true
castle_update_listRename a list or change its colour or description.No findings
Why it is in this group
- The name "castle_update_list" says "update": a word for a change.
- The server marks it destructive (destructiveHint: true).
Description, as the server wrote it
Rename a list or change its colour or description. Castle: PUT /v1/lists/{id}.
Annotations the server declares
- title: Update a list
- destructiveHint: true
castle_update_list_itemChange the comment on a list entry.No findings
Why it is in this group
- The name "castle_update_list_item" says "update": a word for a change.
- The server marks it destructive (destructiveHint: true).
Description, as the server wrote it
Change the comment on a list entry. Castle: PUT /v1/lists/{list_id}/items/{id}.
Annotations the server declares
- title: Update a list item's comment
- destructiveHint: true

Changes things 1Creates or changes something that can be changed back.Claude Code: ask

castle_group_eventsAggregate matching events by one or more fields — the fast way to see which IPs, devices or countries dominate a spike.No findings
Why it is in this group
- Nothing in its name or description says what it does, so it is counted as a write.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Description, as the server wrote it
Aggregate matching events by one or more fields — the fast way to see which IPs, devices or countries dominate a spike. Read-only despite being a POST. Castle: POST /v1/events/group.
Annotations the server declares
- title: Group security events
- readOnlyHint: true

Only reads 7Looks things up and changes nothing.Claude Code: allow

castle_count_list_itemsCount the entries in one list, with the same optional filters as the search.No findings
Why it is in this group
- The name "castle_count_list_items" says "count": a word for reading.
Description, as the server wrote it
Count the entries in one list, with the same optional filters as the search. Read-only despite being a POST. Castle: POST /v1/lists/{list_id}/items/count.
Annotations the server declares
- title: Count items in a list
- readOnlyHint: true
castle_get_events_schemaList the event fields you can filter and group on, with their types.No findings
Why it is in this group
- The name "castle_get_events_schema" says "get": a word for reading.
Description, as the server wrote it
List the event fields you can filter and group on, with their types. Read this first — the other query tools need real field names. Castle: GET /v1/events/schema.
Annotations the server declares
- title: Get the event schema
- readOnlyHint: true
castle_get_listFetch a single list with its primary and secondary field definitions.No findings
Why it is in this group
- The name "castle_get_list" says "get": a word for reading.
Description, as the server wrote it
Fetch a single list with its primary and secondary field definitions. Castle: GET /v1/lists/{id}.
Annotations the server declares
- title: Get one list
- readOnlyHint: true
castle_get_list_itemFetch a single list entry — its value, who added it, the comment and its archive time.No findings
Why it is in this group
- The name "castle_get_list_item" says "get": a word for reading.
Description, as the server wrote it
Fetch a single list entry — its value, who added it, the comment and its archive time. Castle: GET /v1/lists/{list_id}/items/{id}.
Annotations the server declares
- title: Get one list item
- readOnlyHint: true
castle_search_eventsQuery the security event stream — logins, registrations, transactions and their risk verdicts.No findings
Why it is in this group
- The name "castle_search_events" says "search": a word for reading.
Description, as the server wrote it
Query the security event stream — logins, registrations, transactions and their risk verdicts. Read-only despite being a POST: Castle takes the query in the body. Castle: POST /v1/events/query.
Annotations the server declares
- title: Search security events
- readOnlyHint: true
castle_search_list_itemsSearch the entries of one list — the blocked IPs, emails or device ids it holds.No findings
Why it is in this group
- The name "castle_search_list_items" says "search": a word for reading.
Description, as the server wrote it
Search the entries of one list — the blocked IPs, emails or device ids it holds. Read-only despite being a POST. Castle: POST /v1/lists/{list_id}/items/query.
Annotations the server declares
- title: Search items in a list
- readOnlyHint: true
castle_search_listsFind the allow/deny lists defined in the environment.No findings
Why it is in this group
- The name "castle_search_lists" says "search": a word for reading.
Description, as the server wrote it
Find the allow/deny lists defined in the environment. Read-only despite being a POST. Castle: POST /v1/lists/query.
Annotations the server declares
- title: Search lists
- readOnlyHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 1.16.3. Values in angle brackets are yours to fill in.

claude mcp add --transport http castle https://castle.usefulapi.io/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json

{
  "permissions": {
    "allow": [
      "mcp__castle__castle_get_events_schema",
      "mcp__castle__castle_search_events",
      "mcp__castle__castle_search_lists",
      "mcp__castle__castle_get_list",
      "mcp__castle__castle_search_list_items",
      "mcp__castle__castle_count_list_items",
      "mcp__castle__castle_get_list_item"
    ],
    "ask": [
      "mcp__castle__castle_group_events"
    ],
    "deny": [
      "mcp__castle__castle_create_list",
      "mcp__castle__castle_update_list",
      "mcp__castle__castle_create_list_item",
      "mcp__castle__castle_update_list_item",
      "mcp__castle__castle_archive_list_item",
      "mcp__castle__castle_unarchive_list_item"
    ]
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as castle. Review it before you use it.

Keep track

Get told when this server's tools change: a new tool, a new description, a new class.

https://anlyon.dev/servers/io.usefulapi/castle/changes.xml

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Anlyon alternative

7 of these tools change something. Run those as governed actions.

Declare what an action changes, and Anlyon puts it under a shared limit, binds every approval to the exact request, and grades the outcome. It works on any HTTPS API you can describe as an action.

Anlyon does not run, proxy or govern this MCP server. A tool your own code calls directly is not routed through Anlyon and is not governed by it.

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Source: MCP Registry · repository. Synced Oct 21, 2026, 19:23 UTC.

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