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.
curl -O https://raw.githubusercontent.com/alexanderhupfer/fastdomaincheck-mcp-server/main/CLAUDE.mdgit clone --depth 1 https://github.com/alexanderhupfer/fastdomaincheck-mcp-serverWrote 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.
[](https://agentmods.dev/instructions/alexanderhupfer/fastdomaincheck-mcp-server/claude-md)<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.
<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>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 | $0.00246 | $0.00246 |
| Sonnet 5 | $0.00098 | $0.00098 |
| Haiku 4.5 | $0.00049 | $0.00049 |
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 9d 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.
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_domainstool 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
- Tool name:
-
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 implementationwhois: WHOIS query librarypunycode: IDN domain handlingexpress: Health check serveryargs: Command-line argument parsing
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.
- 9d ago First seen · 67 lines · 492 tokens per session scan A 03fe1048821e
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 $0.0025 per session on Opus 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.
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