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Agent skill

Domain Checker

by davidondrej in davidondrej/skills

Check domain registration in batches using public RDAP APIs, without keys or login.

MITAuto-check passed

Install Domain Checker

skills CLI
$ npx skills add davidondrej/skills --skill domain-checker -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install davidondrej/skills domain-checker --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/davidondrej/skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/research-and-web/domain-checker .claude/skills/domain-checker && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
domain-checker
GitHub stars
4.1k
Token cost
~587 tokens
SKILL.md length
261 words
Files
3 (incl. scripts)
Skills in repo
51
Repo updated
First seen
Licence
MIT

At a glance

Check domain registration in batches using public RDAP APIs, without keys or login.

  • Explicitly invokes /domain-checker
  • Runs Python scripts from its folder; calls python3

What it does

Domain Checker is an agent skill from davidondrej/skills. Check domain registration in batches using public RDAP APIs, without keys or login. Use only when the user explicitly invokes /domain-checker.

Its SKILL.md is about 590 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including scripts (for example `agents/openai.yaml` and `scripts/check_domains.py`).

The repository describes itself as: access to david ondrej's personal agent skills. The licence is MIT.

When your agent uses it

  • Explicitly invokes /domain-checker

Example prompts

  • “/domain-checker”

Requirements

  • Python 3

What it can do on your machine

Read from SKILL.md and the folder at commit 387c2b8. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • python3

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • data.iana.org
    • rfc-editor.org
    • about.rdap.org

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Domain Checker loads about 587 tokens when it runs. Until then it costs about 39 tokens; SKILL.md has 261 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~39
When it runs · the whole SKILL.md, loaded when a task matches
~587

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from davidondrej/skills at commit 387c2b8, republished under its MIT licence (© davidondrej). 261 words, ~587 tokens.

Download SKILL.mdSave it as .claude/skills/domain-checker/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
domain-checker
description
Check domain registration in batches using public RDAP APIs, without keys or login. Use only when the user explicitly invokes /domain-checker.
disable-model-invocation
true

Domain checker

Run the bundled Python 3 checker without packages, credentials or a browser. Resolve scripts/check_domains.py relative to this SKILL.md, regardless of the working directory.

sh
python3 <skill-dir>/scripts/check_domains.py example.com example.dev example.ai --json

Use complete domains, not bare brand names or URLs; expand each name/TLD combination. Only domains directly under a TLD are supported (e.g. .com, .dev, .ai, .cloud), not multi-label suffixes such as .co.uk.

The script discovers endpoints through IANA and queries public registries, not registrar shopping carts. Use small batches; concurrency is capped at 4 requests.

Read the results

JSON output is an array of {domain, status, detail} objects. Without --json, output is a short list and elapsed time.

  • REGISTERED: matching registration record found.
  • NOT_FOUND: registry reports no record. Not confirmed available: reservations, registration rules or premium pricing may prevent purchase.
  • UNAVAILABLE: registry explicitly reports a reservation or registration restriction.
  • UNKNOWN: unsupported registry, malformed response, timeout or HTTP error. Never treat as available.
  • INVALID: malformed name or input outside the helper’s scope.

Report briefly as a live snapshot, preserving exact domains and statuses. Explain UNKNOWN reasons. On rate limits, wait before retrying; do not increase concurrency. Bootstrap failure exits nonzero: no checks completed.

Read registry error bodies: a 404 may report a reservation, while Verisign may return an empty RDAP 404. The helper handles both but detects only some reservation wording. Neither DNS absence nor RDAP redirect-service errors prove availability.

Use a registrar for final purchase availability or premium quotes. Registration checks do not establish whether another company uses the name or provide trademark clearance.

Sources: IANA registry discovery, RDAP HTTP semantics, RDAP.org status and rate-limit distinctions.

© davidondrej, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (scripts) in skills/research-and-web/domain-checker of davidondrej/skills.

  • SKILL.md
  • agents/openai.yaml
  • scripts/check_domains.py

Open the folder on GitHubat commit 387c2b8

Compare with similar skills

Domain Checker next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Domain Checker compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Domain Checker this skilldavidondrej/skills4.1k—~587Automated safety check: PassMIT
Batchasgeirtj/system_prompts_leaks69k—~1.3kAutomated safety check: PassCC0-1.0
Batchcodewhale-hq/Codewhale41k—~157Automated safety check: PassMIT
Sitemap Domainthedaviddias/Front-End-Checklist74k—~531Automated safety check: PassMIT
Domain Driven Designdavila7/claude-code-templates33k5 repos~623Automated safety check: PassMIT
Comment Checkercode-yeongyu/oh-my-openagent70k—~160Automated safety check: PassCustom licence

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Questions about Domain Checker

What does Domain Checker do?

Check domain registration in batches using public RDAP APIs, without keys or login. Domain Checker is an agent skill from davidondrej/skills. Check domain registration in batches using public RDAP APIs, without keys or login.

When should I use Domain Checker?

Domain Checker fits situations like: explicitly invokes /domain-checker.

How do I install Domain Checker in Claude Code?

Run `npx skills add davidondrej/skills --skill domain-checker -a claude-code`. Or copy the skill folder (skills/research-and-web/domain-checker in davidondrej/skills) into .claude/skills/domain-checker in your project. Claude Code loads it when a task matches its description.

How do I install Domain Checker in Codex?

Run `npx skills add davidondrej/skills --skill domain-checker -a codex`. Or copy the skill folder (skills/research-and-web/domain-checker in davidondrej/skills) into .agents/skills/domain-checker in your project. Codex loads it when a task matches its description.

Can I use Domain Checker in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add davidondrej/skills --skill domain-checker -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/domain-checker, .gemini/skills/domain-checker, .github/skills/domain-checker and .opencode/skills/domain-checker in your project.

What does Domain Checker need to run?

Going by SKILL.md and its folder, Domain Checker needs Python for the scripts in its folder and the command-line tools its instructions call (python3). Our summary lists: Python 3.

Does Domain Checker access the network?

SKILL.md names 3 domains. As links in the text: data.iana.org, rfc-editor.org and about.rdap.org. This is read from the text; nothing was executed.

Is Domain Checker safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Domain Checker use?

Domain Checker is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Domain Checker use?

About 587 tokens (SKILL.md is roughly 2.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Domain Checker?

Skills that share tags, products or a category with Domain Checker: Batch (asgeirtj/system_prompts_leaks, 69k stars), Batch (codewhale-hq/Codewhale, 41k stars), Sitemap Domain (thedaviddias/Front-End-Checklist, 74k stars) and Domain Driven Design (davila7/claude-code-templates, 33k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Domain Checker?

davidondrej (a GitHub user) maintains it in davidondrej/skills, which has 4,112 GitHub stars. The repository holds 51 skills in this directory. The repository was last updated on October 10, 2026.

Source: davidondrej/skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.