Castle MCP by usefulapi

Castle MCP by usefulapi

Investigate security events and manage the allow/deny lists an analyst acts on. Hosted, no local install.

Live endpoint: https://castle.usefulapi.io/mcp · Homepage: https://usefulapi.io

Connect

• Claude (claude.ai, Desktop): open Customize → Connectors, click + Add → Add custom connector, and paste https://castle.usefulapi.io/mcp.
• Claude Code: claude mcp add --transport http castle https://castle.usefulapi.io/mcp, then run /mcp to log in.
• VS Code: Add to VS Code.
• Cursor and other clients: add the URL as a remote MCP server:

{
  "mcpServers": {
    "castle": {
      "url": "https://castle.usefulapi.io/mcp"
    }
  }
}

Add only the URL. Do not add an Authorization header or an API key to the client config: the server signs you in with OAuth, and the login page asks for your Castle credentials.

Step-by-step setup, where to find your credentials, and FAQ: https://usefulapi.io/castle/

On first connect you'll paste your Castle credentials. They are validated, stored per-user, and scoped to you — no keys in config files.

Tools

Tool	Type	What it does
castle_get_events_schema	read	Get the event schema
castle_search_events	read	Search security events
castle_group_events	read	Group security events
castle_search_lists	read	Search lists
castle_get_list	read	Get one list
castle_search_list_items	read	Search items in a list
castle_count_list_items	read	Count items in a list
castle_get_list_item	read	Get one list item
castle_create_list	write	Create a list
castle_update_list	write	Update a list
castle_create_list_item	write	Add an item to a list
castle_update_list_item	write	Update a list item's comment
castle_archive_list_item	write	Archive a list item
castle_unarchive_list_item	write	Unarchive a list item
castle_usage_status	meta	Usage status (free-tier meter)
castle_request_feature	meta	Request a missing feature
castle_upgrade	meta	Upgrade to Pro (unlimited*)
castle_cancel_subscription	meta	Cancel the Pro subscription

read tools are read-only; write tools mutate data (clients should confirm them); meta tools report usage, manage your subscription or send a feature request.

Pricing

Plan	Price	Limit
Free	$0	50 tool calls / month
Pro	$9/mo or $90/yr (2 months free)	Unlimited*

*Pro has a fair use limit of 10,000 tool calls a month on this server. For more, write to [email protected].

Pro covers this server only. Subscribe with castle_upgrade (it returns a Stripe Checkout link). Cancel any time with castle_cancel_subscription: Pro continues to the end of the paid period, with no refund for the current period, and running castle_upgrade before then undoes the cancel. Or write to [email protected].

License

MIT