Hacker News Reader

There is, but I can't remember the link, haha. You just kinda learn things over the years. This one can be reached by clicking on the domain name of a linked article, so it's easy to remember how to get there.

There is a guide to the API here: https://github.com/HackerNews/API

Specifically for search, might as well use hn.algolia.com than figure out how to use HN's hidden(ish) API.