This is a delightfully focused little project: a Model Context Protocol (MCP) server that exposes a handful of classic payments-domain validation utilities as tools an LLM can call. Think Luhn checksum validation for credit cards, card-brand detection (Visa, Mastercard, Amex, etc.), and IBAN validation for international bank accounts — all wrapped in the MCP interface so any MCP-aware client (Claude Desktop, Cursor, custom agents) can invoke them.

Why is that interesting? A few reasons:

• It's a clean, minimal MCP example. Most MCP servers in the wild are either sprawling integrations with commercial APIs or toy "hello world" repos. A payments-validation server sits in a sweet spot — the domain logic is well-understood, the tools have clear inputs and outputs, and the whole thing is small enough to read in one sitting. That makes it a great reference for anyone learning how to structure an MCP server in TypeScript.
• The problem domain is genuinely useful. Luhn and IBAN checks are the kind of thing developers reimplement badly every few years. Exposing them as agent-callable tools means an LLM can sanity-check user-provided card or bank data before shoving it into a downstream system.
• The author calls it a learning project, which usually means the code is written to be understood rather than to impress. That's exactly what you want when picking apart a new protocol.

Who would benefit? Developers exploring MCP who want a bite-sized reference implementation in TypeScript; anyone building fintech-adjacent AI agents who needs battle-tested validation primitives; and educators looking for a tidy example of "wrap a pure-function library as an MCP server."

Zero stars today, but this is exactly the kind of repo that quietly becomes a template people copy from for years.