FernTool — network toolbox MCP server & free IP API

FernTool is a fast, clean "what is my IP" and IP lookup tool. This repo documents its hosted, remote MCP server so AI assistants and agents (Claude, Cursor, VS Code Copilot and others) can:

• get the caller's public IP, ISP, ASN, location and timezone
• look up the country, ASN and network owner of any IPv4/IPv6 address
• detect Tor exit nodes, VPN/datacenter and cloud IPs (AWS, Google Cloud, Azure, Cloudflare, DigitalOcean, Oracle, Hetzner, OVH and more)
• batch look up to 100 IPs in one call
• run WHOIS (RDAP) for domains, IPs and ASNs, DNS lookups (A/AAAA/MX/TXT/NS/CNAME/SOA), reverse DNS and IPv4/IPv6 subnet math
• validate and classify IP addresses (public, private, loopback, documentation and so on)

No API key, no install, no sign-up. It's just a URL:

https://www.ferntool.com/mcp

Transport: MCP streamable HTTP (JSON-RPC 2.0, protocol 2025-06-18).

Connect

Claude Code

claude mcp add --transport http ferntool https://www.ferntool.com/mcp

Claude Desktop (claude_desktop_config.json). Use Settings → Connectors → Add custom connector with the URL above, or bridge with mcp-remote:

{ "mcpServers": { "ferntool": { "command": "npx", "args": ["-y", "mcp-remote", "https://www.ferntool.com/mcp"] } } }

Cursor (~/.cursor/mcp.json or .cursor/mcp.json)

{ "mcpServers": { "ferntool": { "url": "https://www.ferntool.com/mcp" } } }

VS Code (.vscode/mcp.json)

{ "servers": { "ferntool": { "type": "http", "url": "https://www.ferntool.com/mcp" } } }

Ready-made files are in examples/.

Tools

Tool	Input	What it returns
get_my_ip	none	Public IP of the caller (IPv4 or IPv6) with ISP, ASN, city/region/country, coordinates, timezone and is_tor / is_datacenter / provider. For remote agents, this is the IP of the machine calling the server.
lookup_ip	ip (string, IPv4 or IPv6)	Validity, version, scope, country, timezone, ASN, network owner and flags (is_tor, is_datacenter, provider).
batch_lookup_ip	ips (array of 1–100 strings)	lookup_ip results for every address, plus complete / retry.
validate_ip	ip (string)	Whether it's a valid IPv4/IPv6, the expanded form and the scope (public/private/loopback/link-local/documentation/...).
whois_lookup	query (domain, IP or ASN like AS13335)	RDAP record: registrar, created/expiry/updated dates, status, nameservers, DNSSEC; for IPs/ASNs the network name, range/CIDR, owner org, country and abuse contact.
dns_lookup	domain, optional types (A, AAAA, MX, TXT, NS, CNAME, SOA)	Records with TTLs via Cloudflare 1.1.1.1 DNS-over-HTTPS, response status and DNSSEC validation flag.
reverse_dns	ip	PTR hostname(s) and whether the hostname resolves back to the IP (forward-confirmed).
subnet_calc	cidr (e.g. 192.168.1.0/24, 2001:db8::/48)	Network, netmask, wildcard, broadcast, first/last usable, total and usable addresses, block type.

Example lookup_ip result for 8.8.8.8:

{
  "valid": true, "version": 4, "ip": "8.8.8.8", "scope": "public",
  "source": "dbip-lite+iptoasn",
  "geo": { "country": "US", "country_name": "United States", "asn": 15169, "isp": "GOOGLE",
           "timezone": "America/New_York", "timezones": ["America/New_York", "..."] },
  "flags": { "is_tor": false, "is_datacenter": true, "provider": "Google Cloud" }
}

Example validate_ip result for 2001:db8::1:

{ "valid": true, "version": 6, "ip": "2001:db8::1",
  "expanded": "2001:0db8:0000:0000:0000:0000:0000:0001", "scope": "documentation" }

Raw JSON-RPC

curl -s https://www.ferntool.com/mcp \
  -H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"lookup_ip","arguments":{"ip":"8.8.8.8"}}}'

Plain HTTP API

The same data is available without MCP. There's no key, and CORS is *. Full spec: /openapi.json.

curl https://www.ferntool.com/ip              # 203.0.113.7  (plain text)
curl https://www.ferntool.com/json            # your IP + ISP, ASN, city, timezone
curl https://www.ferntool.com/api/ip/1.1.1.1  # any IPv4/IPv6 (+ timezone, Tor/datacenter flags)
curl -X POST https://www.ferntool.com/api/batch -H 'Content-Type: application/json' -d '{"ips":["8.8.8.8","1.1.1.1"]}'
curl https://www.ferntool.com/api/whois/example.com          # RDAP WHOIS (domain, IP or ASN)
curl "https://www.ferntool.com/api/dns/example.com?type=A,MX" # DNS via Cloudflare DoH
curl https://www.ferntool.com/api/reverse-dns/1.1.1.1        # PTR
curl "https://www.ferntool.com/api/subnet?cidr=10.0.0.0/22"   # subnet calculator

Python:

import json, urllib.request
print(json.load(urllib.request.urlopen("https://www.ferntool.com/api/ip/8.8.8.8")))

JavaScript:

const r = await fetch("https://www.ferntool.com/api/ip/8.8.8.8");
console.log(await r.json());

Fair use

This is a free service on a shared edge network. Please cache results and keep traffic reasonable. Network lookups (WHOIS, DNS, reverse DNS, batch) are limited to roughly 40 per minute per IP; heavy or abusive traffic may be rate-limited further.

Data attribution

• IP geolocation by DB-IP, licensed under CC BY 4.0.
• ASN data from IPtoASN (PDDL).
• The caller's own location in get_my_ip comes from the Cloudflare edge.
• Tor exit list from the Tor Project; cloud ranges published by AWS, Google Cloud, Microsoft Azure, Cloudflare, DigitalOcean and Oracle; plus a list of well-known hosting ASNs. Refreshed regularly.
• WHOIS from registry RDAP services (IANA bootstrap); DNS from Cloudflare 1.1.1.1. Timezones for other IPs are the country's main IANA zone (tzdata).

Links

• Website: https://www.ferntool.com
• What is my IP: https://www.ferntool.com/
• IP lookup: https://www.ferntool.com/ip-lookup
• VPN leak test: https://www.ferntool.com/vpn-leak-test
• WHOIS lookup: https://www.ferntool.com/whois-lookup
• DNS lookup: https://www.ferntool.com/dns-lookup
• Reverse DNS: https://www.ferntool.com/reverse-dns
• Subnet calculator: https://www.ferntool.com/subnet-calculator
• MCP registry name: com.ferntool/ip

License

The contents of this repository (docs, examples, server.json) are under the MIT License. The hosted service and its data are subject to the attributions above.