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Castle MCP by usefulapi MCP Server

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Castle MCP by usefulapi is answering right now. Last checked 11 min ago. It exposes 14 tools. Last commit 2 Nov 2026.

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

Uptime history 34 days of history
34 days agonow
100.0%
Uptime 24h
91 of 91 checks
14
Tools
read from the server
165 ms
Response time
average over 24h
1
Stars
last commit 2 Nov 2026

What changed 31

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 7 October 2026. No other catalogue keeps this.

2 Nov a tool changed version
31 Oct a tool changed version4 times that day
30 Oct a tool changed version2 times that day
29 Oct a tool changed version2 times that day
28 Oct a tool changed version2 times that day
27 Oct a tool changed version
25 Oct a tool changed version4 times that day
24 Oct a tool changed version3 times that day
23 Oct a tool changed version
22 Oct a tool changed version
and 21 more, back to 7 October 2026

Nothing serious here today

Today is the operative word: we check Castle MCP by usefulapi every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Three servers free · no card

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 11 min ago.

run in your terminal
claude mcp add castle --transport http https://castle.usefulapi.io/mcp
Settings → Connectors → Add custom connector, then paste this address
https://castle.usefulapi.io/mcp
~/.codex/config.toml
[mcp_servers.castle]
url = "https://castle.usefulapi.io/mcp"
.cursor/mcp.json
{
  "mcpServers": {
    "castle": {
      "url": "https://castle.usefulapi.io/mcp"
    }
  }
}
.vscode/mcp.json
{
  "servers": {
    "castle": {
      "type": "http",
      "url": "https://castle.usefulapi.io/mcp"
    }
  }
}

Available tools 14

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

castle
castle_archive_list_item
Archive a list entry so it stops matching. Reversible with castle_unarchive_list_item. Castle: DELETE /v1/lists/{list_id}/items/{id}/archive.
castle_count_list_items
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.
castle_create_list
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.
castle_create_list_item
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.
castle_get_events_schema
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.
castle_get_list
Fetch a single list with its primary and secondary field definitions. Castle: GET /v1/lists/{id}.
castle_get_list_item
Fetch a single list entry — its value, who added it, the comment and its archive time. Castle: GET /v1/lists/{list_id}/items/{id}.
castle_group_events
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.
castle_search_events
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.
castle_search_list_items
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.
castle_search_lists
Find the allow/deny lists defined in the environment. Read-only despite being a POST. Castle: POST /v1/lists/query.
castle_unarchive_list_item
Restore a previously archived list entry so it matches again. Castle: PUT /v1/lists/{list_id}/items/{id}/unarchive.
castle_update_list
Rename a list or change its colour or description. Castle: PUT /v1/lists/{id}.
castle_update_list_item
Change the comment on a list entry. Castle: PUT /v1/lists/{list_id}/items/{id}.

Endpoints

URLTransportStateLatencyChecked
https://castle.usefulapi.io/mcp streamable-http answering 70 ms 11 min ago

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Castle MCP by usefulapi — questions

Answers built from our own checks of this server.

What can Castle MCP by usefulapi do?
It exposes 14 tools, read directly from the server on our last check. Among them: castle_archive_list_item, castle_count_list_items, castle_create_list, castle_create_list_item, castle_get_events_schema, castle_get_list and 8 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →
Is Castle MCP by usefulapi working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 165 ms. The bar chart above shows every period we have measured.
How do I connect Castle MCP by usefulapi?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.
Does Castle MCP by usefulapi need an API key?
No. Castle MCP by usefulapi completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 14 of them are readable on this page. This is what we observed, not what the docs claim.
How fast is Castle MCP by usefulapi?
It answers our handshake in 165 ms on average, which is faster than 79% of all working MCP servers we measure. That puts it in the quick quarter of the ecosystem. The comparison comes from our own checks across the whole registry, every 15 minutes.
Is Castle MCP by usefulapi open source?
The code is open source: it is published under the MIT licence, written in JavaScript, 1 stars on GitHub and 1 open issue. The licence covers the code in the repository, not the hosted service at castle.usefulapi.io, which runs on its operator's own terms.