whois-mcp-server

Overview

Domain and network intelligence via RDAP and DNS-over-HTTPS. Look up domain registrations, check registry record status, fetch DNS records, and resolve IPs and ASNs to their registries. No API key required.

Tools

The whois-guide covers hostname investigations and tracing DNS addresses to registry allocations and observed origin ASNs. It ships with the plugin and is available to MCP clients as skill://whois-guide/SKILL.md.

Related MCP server: domain-checker

Capability reference

whois_lookup_domain tool

• Takes a Unicode or ASCII fully qualified domain name. Returns the ASCII domain and, for an IDN, unicode_domain as decoded display text.

• Returns registrar, dates, nameservers, EPP status, DNSSEC, and registrant_redacted; DNSSEC and privacy stay null when the registry gives no evidence. Fails with rdap_no_coverage, domain_not_found, or rdap_invalid_domain_response (the response doesn't match the queried domain).

• An exact registry miss can name a registrable parent to query next. Missing RDAP coverage points to DNS evidence, which cannot establish registration status.

• include_registrar: true follows one registrar RDAP referral and adds registrar_detail (found, no_referral, or failed, plus source URL). Off by default; limited by RDAP_TIMEOUT_MS, and a failure keeps the registry result.

whois_check_availability tool

• Takes a Unicode or ASCII fully qualified domain name and returns its ASCII form with optional decoded unicode_domain.

• Returns registration_status: registered | not_found | unknown. available is false for a found registration and null otherwise, never true: a 404 means no record, not that the name can be registered.

• Known ICANN subdomains return non_registrable_domain with their registrable parent.

whois_get_dns tool

• Takes a Unicode or ASCII DNS name, including underscore owners and one terminal root dot. The ASCII lookup name is limited to 253 characters with 1–63-character labels; IDNs also return decoded unicode_domain.

• Optional types: A, AAAA, MX, TXT, NS, CNAME, SOA, CAA, PTR, SRV, DS, DNSKEY, TLSA, HTTPS; defaults to A, AAAA, MX, TXT, NS. Record data retains the resolver's literal presentation.

• Returns records with TTLs and query_sources: [{type, source}], including empty answers and NXDOMAIN. Legacy source is cloudflare if any query got a successful Cloudflare response, otherwise nextdns.

• Resolver failure codes and truncated responses return errors after retries and fallback. CAA queries go to NextDNS.

whois_lookup_ip tool

• Takes an IPv4/IPv6 address with an optional CIDR prefix (0–32 / 0–128). Echoes the original ip.

• Returns org, country, abuse contact, provider CIDRs in cidrs (cidr only when there is exactly one), and a best-effort reverse DNS lookup: ptr_status: found | not_found | failed, with ptr_source_error on failure while the RDAP data is kept.

• Optional registration_date and last_changed preserve the queried object's RDAP timestamps. RIPE maintainer handles are excluded from org_name; missing organization evidence stays omitted.

• include_routing: true adds routing (found | not_found | failed) with the RIS-observed prefix and origin_asns, from RIPEstat Network Info. Off by default; a routing failure keeps the RDAP and PTR results.

• Fails with invalid_ip, ip_not_found, ip_no_rdap_route (no RIR covers the address; not retryable), or private_range for 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, ::1/128, fc00::/7, and fe80::/10.

whois_lookup_asn tool

• Takes an ASN from 1 to 4294967295, with an optional AS prefix (e.g., AS15169, AS 15169, +15169). Out-of-range numbers fail with invalid_asn.

• Returns name, org_name, country, rir, start_autnum, and end_autnum, plus abuse_email, registration_date, and last_changed when the record carries them. Fails with asn_not_found when no record exists.

whois_get_dossier tool

• Takes a Unicode or ASCII hostname and runs registration and A/MX/NS/TXT lookups in parallel. After an exact registry 404, it can try the ICANN registrable parent and identify it as registration_domain; DNS stays on the supplied hostname.

• Returns registration, DNS, domain age, privacy status, and inferred NS/MX providers. A failed lookup leaves the other's data in place and sets rdap_source_error or dns_source_error; both_legs_failed means neither succeeded.

• NS/MX provider inference uses the first record. Unknown-provider labels come from the registrable hostname, including multi-label suffixes such as co.uk.

• A null MX (0 .) means the domain accepts no mail.

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, optional RIPEstat Network Info) 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 is true when the registry shows it and null when there's no evidence

• Partial failure model — whois_get_dossier marks a failed lookup with a source_error field and continues; only both failing is 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://127.0.0.1:3010/mcp

Prerequisites

• Bun v1.4.4 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.

The default log directory and relative LOGS_DIR paths resolve from the installed server package. Set an absolute LOGS_DIR to log elsewhere.

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.