What is fastdomaincheck-mcp-server CLAUDE.md?

A CLAUDE.md instruction file for FastDomainCheck MCP Server, a Node.js service that checks whether domain names can be registered. It describes the project structure, commands, and design.

Use it when installing dependencies, running or developing the server, or changing its domain-checking and MCP code.

It gives a coding agent the project context needed to work consistently in that repository.

How alexanderhupfer/fastdomaincheck-mcp-server configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to alexanderhupfer/fastdomaincheck-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/alexanderhupfer/fastdomaincheck-mcp-server/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/alexanderhupfer/fastdomaincheck-mcp-server

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md/github.svg)](https://agentmods.dev/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md"><img src="https://agentmods.dev/badge/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 492 This file is loaded in full into every session.

When invoked 492 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00492	$0.00492
Opus 5.5	$0.00197	$0.00197
Sonnet 5.5	$0.00098	$0.00098
Haiku 4.5	$0.00049	$0.00049

Measured 2mo ago against content hash 03fe1048821e, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

fastdomaincheck-mcp-server CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

CLAUDE.md · 67 lines

What it actually says

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

FastDomainCheck MCP Server is a Model Context Protocol (MCP) server that provides bulk domain name registration status checking. It's written in JavaScript/Node.js and uses the @modelcontextprotocol/sdk package.

Core Architecture

The codebase follows a simple modular structure:

index.js: Entry point that registers the check_domains tool with MCP framework and handles STDIO communication
lib/checker.js: Core domain checking logic using dual verification (WHOIS queries with DNS fallback)
lib/config.js: TLD-to-WHOIS server mappings and unregistered domain detection patterns

The server communicates via STDIO using the MCP protocol, allowing AI tools to check domain availability for 200+ TLDs including IDN and Chinese domains.

Common Development Commands

# Install dependencies
npm install

# Run the server
npm start

# Run with health check enabled (for testing/debugging)
node index.js --health-check --health-check-port 8080

# Run in development mode with auto-reload
npm run dev

Key Implementation Details

Domain Checking Flow:
- Input validation (length 1-253 chars, valid format)
- WHOIS query to authoritative server (10s timeout)
- Fallback to DNS resolution if WHOIS fails
- Returns simplified JSON with domain status
MCP Tool Registration:
- Tool name: check_domains
- Accepts array of domains (max 50)
- Returns JSON array with availability status
Performance Characteristics:
- Sequential processing (0.3-1 second per domain)
- No caching or concurrent checking
- 10-second timeout per WHOIS query

Testing Approach

Currently no tests exist. When adding tests, focus on:

Domain validation logic
WHOIS response parsing for different TLDs
Fallback mechanism behavior
MCP tool integration

Dependencies

@modelcontextprotocol/sdk: MCP framework implementation
whois: WHOIS query library
punycode: IDN domain handling
express: Health check server
yargs: Command-line argument parsing

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 67 lines · 492 tokens per session scan A 03fe1048821e

Subscribe to this mod's changes

fastdomaincheck-mcp-server CLAUDE.md is an instructions file published in the GitHub repository alexanderhupfer/fastdomaincheck-mcp-server (0 stars, last pushed 1y ago), licensed MIT. It adds 492 tokens to every session, about $0.0020 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

fastdomaincheck-mcp-server CLAUDE.md next to 6 instructions from other repositories
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fastdomaincheck-mcp-server: Instructions file for Claude Code