How do I install the Check Domain skill?

Run npx skillmds@latest add mfraunhofer/check-domain in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Check Domain safe to use?

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Which AI agents work with Check Domain?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Check Domain free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Check Domain?

mfraunhofer (@mfraunhofer) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Check Domain by mfraunhofer — Agent Skill

Name: Check Domain
Author: mfraunhofer

Check Domain

Check domain availability with a whois lookup against the official registrars (DENIC for .de, EURid for .eu, Verisign for .com/.net, PIR for .org). Use when checking if a domain is available, during brand/naming research, or before registering a new domain.

mfraunhofer fe81d0e 3 files · 9.1 KB Updated Sep 17, 2026

File contents

Check Domain Availability

Check whether domain names are available for registration. Uses the system whois command directly against official registrars for reliable results, no third-party libraries or lookup sites.

When to use

Checking if a domain is available
Brand/naming research where domain availability matters
Before registering a new domain

Requirements

The system whois command. No API keys.

macOS: brew install whois (or preinstalled)
Debian/Ubuntu: apt install whois

Usage

Check a single domain:

python3 ~/.claude/skills/check-domain/scripts/check_domain.py example.de

Check multiple domains:

python3 ~/.claude/skills/check-domain/scripts/check_domain.py example.de example.com example.eu example.org

Check one name across all major TLDs (.de .com .eu .org .net):

python3 ~/.claude/skills/check-domain/scripts/check_domain.py --all mybrand

Output:

mybrand.de         FREE
mybrand.com        TAKEN  (registered: 2019-06-28, expires: 2026-06-28)
mybrand.eu         FREE

How it works

Calls the whois CLI directly (not the python-whois library, which is unreliable for .de domains)
Parses the raw WHOIS response per TLD:
- .de (DENIC): Status: free = available
- .com/.net (Verisign): No match for = available
- .eu (EURid): Status: AVAILABLE = available
- .org (PIR): NOT FOUND = available
Returns registration dates where the registrar exposes them

Notes

Do NOT use the python-whois pip package for .de domains: its error text can contain Status: free even when the domain IS registered, and it sometimes reports registered domains as free.
Do NOT use third-party WHOIS sites (who.is, whois.com): they cache results and can be wrong.
Always use the system whois command, which queries the official registrars directly. For .de, DENIC (whois.denic.de) is the only authoritative source; for .eu, EURid.

---name: check-domaindescription: Check domain availability with a whois lookup against the official registrars (DENIC for .de, EURid for .eu, Verisign for .com/.net, PIR for .org). Use when checking if a domain is available, during brand/naming research, or before registering a new domain.---# Check Domain AvailabilityCheck whether domain names are available for registration. Uses the system `whois` command directly against official registrars for reliable results, no third-party libraries or lookup sites.## When to use- Checking if a domain is available- Brand/naming research where domain availability matters- Before registering a new domain## RequirementsThe system `whois` command. No API keys.- macOS: `brew install whois` (or preinstalled)- Debian/Ubuntu: `apt install whois`## UsageCheck a single domain:```bashpython3 ~/.claude/skills/check-domain/scripts/check_domain.py example.de```Check multiple domains:```bashpython3 ~/.claude/skills/check-domain/scripts/check_domain.py example.de example.com example.eu example.org```Check one name across all major TLDs (.de .com .eu .org .net):```bashpython3 ~/.claude/skills/check-domain/scripts/check_domain.py --all mybrand```Output:```mybrand.de FREEmybrand.com TAKEN (registered: 2019-06-28, expires: 2026-06-28)mybrand.eu FREE```## How it works- Calls the `whois` CLI directly (not the `python-whois` library, which is unreliable for .de domains)- Parses the raw WHOIS response per TLD: - .de (DENIC): `Status: free` = available - .com/.net (Verisign): `No match for` = available - .eu (EURid): `Status: AVAILABLE` = available - .org (PIR): `NOT FOUND` = available- Returns registration dates where the registrar exposes them## Notes- Do NOT use the `python-whois` pip package for .de domains: its error text can contain `Status: free` even when the domain IS registered, and it sometimes reports registered domains as free.- Do NOT use third-party WHOIS sites (who.is, whois.com): they cache results and can be wrong.- Always use the system `whois` command, which queries the official registrars directly. For .de, DENIC (whois.denic.de) is the only authoritative source; for .eu, EURid.

Frequently asked questions