Arcnautical

@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.

[Smithery] [npm] [Wellknown: live]

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/mcpclaude 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 new key includes a one-time free allowance of vessel screenings and a monthly allowance of voyage assessments; get_usage reports both, and the current numbers are on arcnautical.com/developers.

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 installnpm 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