@arcnautical/mcp

An MCP server for the ArcNautical API: screen any commercial vessel by IMO number for sanctions, ownership opacity and a vetting grade — from Claude, ChatGPT, Cursor, VS Code, Windsurf or any MCP client.

Two tools need no API key at all. Add it, ask "is IMO 9274446 sanctioned?", get the answer.

Two ways to use it: a remote endpoint at https://mcp.arcnautical.com/mcp (nothing to install — claude.ai, ChatGPT, Claude Code, Cursor) or a local server over stdio with npx -y @arcnautical/mcp (Claude Desktop and every other stdio client).

IMO 9274446 HS STAR: sanctions RED — 4 confirmed matches on vessel identifier.
Ownership opacity MEDIUM. Vetting grade E (unacceptable). Checked 2026-09-12T08:10:40Z.

Remote endpoint (no install)

https://mcp.arcnautical.com/mcp — MCP Streamable HTTP, stateless, JSON responses. No authentication is required for check_vessel and find_port; the keyed tools take your API key as an Authorization: Bearer header on the MCP request (an X-API-Key or arcnautical-api-key header is accepted too, for gateways that name the header themselves — never a query parameter).

claude.ai — Settings → Connectors → Add custom connector → URL https://mcp.arcnautical.com/mcp, no authentication. The two keyless tools are available at once.

ChatGPT — Settings → Connectors → Create (developer mode) → server URL https://mcp.arcnautical.com/mcp, no authentication.

Claude Code

claude mcp add --transport http arcnautical https://mcp.arcnautical.com/mcp
claude mcp add --transport http arcnautical https://mcp.arcnautical.com/mcp --header "Authorization: Bearer arc_live_…"

Cursor — .cursor/mcp.json:

{
  "mcpServers": {
    "arcnautical": {
      "url": "https://mcp.arcnautical.com/mcp",
      "headers": { "Authorization": "Bearer arc_live_…" }
    }
  }
}

Anything with curl — the endpoint is plain JSON-RPC over POST:

curl -s https://mcp.arcnautical.com/mcp -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_vessel","arguments":{"imo":"9274446"}}}'

The remote endpoint is a thin client of the same public API: a keyless call counts against your 100-per-hour allowance (the caller's address is forwarded), and a keyed call is metered on your key exactly as a direct API call would be. GET /mcp answers 405 — there is no server-to-client stream to hold — and GET https://mcp.arcnautical.com/health reports the endpoint's version.

Local server (stdio)

Requires Node 18+. No install step — every client below runs it with npx.

Claude Desktop — claude_desktop_config.json:

{
  "mcpServers": {
    "arcnautical": {
      "command": "npx",
      "args": ["-y", "@arcnautical/mcp"]
    }
  }
}

Claude Code

claude mcp add arcnautical -- npx -y @arcnautical/mcp

Cursor / Windsurf / VS Code — same command / args shape in the client's MCP settings.

To unlock the full record, batches and voyage scoring, add an API key to the env block:

{
  "mcpServers": {
    "arcnautical": {
      "command": "npx",
      "args": ["-y", "@arcnautical/mcp"],
      "env": { "ARCNAUTICAL_API_KEY": "arc_live_…" }
    }
  }
}

Keys are free and self-serve at https://arcnautical.com/get-a-key?from=mcp — no card, no approval step. A key includes 5,000 vessel screenings and 10,000 voyage assessments a month.

Tools

Reading a verdict

• RED — confirmed match on the vessel identifier. AMBER — possible match, review it. GREEN — no match against the sources reached. INCOMPLETE — a core source could not be read; never present it as clear.
• coverage_complete: false on a GREEN means one supplementary list was unavailable: re-screen before relying on it.
• assessed: false means ownership and vetting are defaults, not findings.
• The keyless check matches the vessel's current name and identifiers only. A hull renamed after a designation can read GREEN there; screen_vessel covers that case.
• Designations change daily. Quote the checkedAt / screened_at time with any answer.

Idempotency

Every resource-creating call sends an Idempotency-Key derived from the question — the hull and the UTC day — not from the attempt. Asking about the same vessel twice in a day returns the stored record and spends nothing. The API's docs measured 42% of one integration's monthly screenings as same-day repeats billed only because their client generated a random key per call; this server does not do that.

Environment

Self-hosting the HTTP endpoint

npx -y @arcnautical/mcp --http serves POST /mcp on port 3005 — useful when your assistants run in a network that cannot spawn local processes but can reach one internal URL. The Dockerfile in this repository builds the same thing; it is what mcp.arcnautical.com runs.

Links

• Guide: https://arcnautical.com/developers/
• Reference: https://arcnautical.com/developers/reference/
• OpenAPI 3.1: https://arcnautical.com/api/v1/openapi.json
• Postman: https://www.postman.com/arcnautical-6322764/arcnautical-s-workspace
• For agents: https://arcnautical.com/llms.txt
• Listed on: MCP registry (com.arcnautical/mcp) · Smithery · npm · Wellknown (verified owner; live reachability checks)

Development

npm install
npm test        # builds, then drives dist/cli.js over stdio AND createHttpServer() over Streamable HTTP
                # (a local stub API asserts the forwarded caller address and Bearer key; one call hits prod keyless)
npm run start:http   # the remote endpoint on http://localhost:3005/mcp

MIT © ArcNautical