whois-mcp-server

Overview

Domain and network intelligence via RDAP and DNS-over-HTTPS. Look up domain registrations, check availability, fetch DNS records, and resolve IPs and ASNs to their registries — all via public, keyless data sources. Runs as a stdio process or a local Streamable HTTP server.

Tools

Related MCP server: domain-checker

Capability reference

whois_lookup_domain tool

• Accepts a fully qualified domain name and selects the registry RDAP server through IANA bootstrap.

• Returns registrar, registration dates, nameservers, EPP status, DNSSEC, and registrant_redacted; throws rdap_no_coverage or domain_not_found when no record can be returned.

whois_check_availability tool

• Accepts a fully qualified domain name for a registration check.

• Returns available: true for RDAP 404, false with registrar and expiry for a registered domain, or null with rdap_coverage: false when coverage is absent.

whois_get_dns tool

• Accepts a hostname and optional nonempty types: A, AAAA, MX, TXT, NS, CNAME, SOA, CAA, PTR; omission defaults to A, AAAA, MX, TXT, NS. Duplicate types are queried once.

• Returns records with TTLs and ordered query_sources: [{type, source}], including empty answers and NXDOMAIN. Legacy source is cloudflare if any query consumed a successful Cloudflare response, otherwise nextdns; a nonexistent domain returns nxdomain: true as data.

whois_lookup_ip tool

• Accepts a complete IPv4/IPv6 address with at most one decimal CIDR prefix (0–32 / 0–128); no whitespace, zone IDs, or brackets. Queries the base address and echoes the original ip. IPv4-mapped IPv6 uses the embedded IPv4 for policy, RDAP, and PTR; other IPv6 uses 32 reversed PTR nibbles.

• Returns netblock CIDR, organization, country, abuse contact, and best-effort PTR (null on failure); throws invalid_ip for malformed input or ip_not_found on an RIR RDAP 404.

• private_range enforces an explicit policy: IPv4 0.0.0.0/8, 10.0.0.0/8, 100.64.0.0/10, 127.0.0.0/8, 169.254.0.0/16, 172.16.0.0/12, 192.168.0.0/16, 255.0.0.0/8; IPv6 ::1/128, fc00::/7, fe80::/10. Other special-use addresses remain eligible for registry records or normal no-coverage/not-found outcomes.

whois_lookup_asn tool

• Accepts a decimal ASN from 1 to 4294967295 with an optional case-insensitive AS prefix and leading + (e.g., AS15169, AS 15169, +15169). Outer whitespace and whitespace after AS are allowed; whitespace inside digits or after +, suffixes, decimals, and out-of-range values return invalid_asn.

• Returns name, org_name, country, rir, start_autnum, and end_autnum; throws asn_not_found when no ASN record exists.

whois_get_dossier tool

• Accepts a fully qualified domain name for parallel registration and A/MX/NS/TXT lookups.

• Returns registration, DNS, domain age, privacy status, and inferred NS/MX providers. Individual failures remain partial data in rdap_source_error or dns_source_error; both_legs_failed means neither source succeeded.

Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

RDAP / DNS-specific:

• RDAP over HTTPS — no port-43 TCP dependency

• IANA bootstrap auto-selection — correct registry RDAP server picked per TLD, RIR, or ASN range; bootstrap JSON cached in-memory for 24h

• DNS-over-HTTPS via Cloudflare and NextDNS — dual-provider with per-type routing (NextDNS for CAA; Cloudflare for all others) and automatic fallback

• No API keys required — all sources (IANA, registry RDAP endpoints, RIR RDAP, Cloudflare DoH, NextDNS DoH) are public and keyless

Agent-friendly output:

• Coverage signaled two ways — rdap_coverage: false returned as data by whois_check_availability and whois_get_dossier, while whois_lookup_domain throws rdap_no_coverage for the same case

• Privacy redaction surfaced as a field — registrant_redacted: true rather than silently absent contact data

• Partial failure model — whois_get_dossier marks individual legs with a source_error field and continues; only both-legs-fail escalates to an error

• Factual signals, not scores — age_days, privacy_redacted, ns_provider, mx_provider are real data, not synthesized risk scores

Getting started

No API keys or accounts required. Add the following to your MCP client configuration file.

{
  "mcpServers": {
    "whois-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/whois-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "whois-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/whois-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "whois-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "ghcr.io/cyanheads/whois-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).

• No API keys required — all data sources are public.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/whois-mcp-server.git

2. Navigate into the directory:

cd whois-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

cp .env.example .env
# All vars are optional — defaults work for most use cases

Configuration

See .env.example for the full list of optional overrides.

Running the server

Local development

• Build and run:

  bun run rebuild
  bun run start:stdio
  # or
  bun run start:http

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec

Docker

docker build -t whois-mcp-server .
docker run --rm -p 3010:3010 whois-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/whois-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Development guide

See CLAUDE.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic

• Use ctx.log for request-scoped logging

• Register new tools via src/app.ts's tools array

• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.