Korea's National Tax Service runs a clean public API for business registration status. Give it a 10-digit number, get back whether the company is active, suspended or closed. It's free, it's fast, it's accurate.

It also has no memory.

Ask it today and you learn the company is closed. Ask what it was last month and there's no answer, because that question isn't in the API. There's no as_of parameter, no history endpoint, no changelog. The present tense is the only tense available.

That gap turned out to be the most interesting thing I've found while building an API for AI agents, so I did the obvious thing: I started writing down what I saw, every day.

What I built

A scheduled job, running once a day, that asks for the current status of every company in a fixed list and stores the answer.…