I agree that search is a key direction for growth in this tooling ecosystem. I don't think a tool should index every visited webpage though. I think knowledge base construction should be intentional and methodology, as the process provides its own value.

I’ve begun building a knowledge base that is built around a Google-search interface but with closed-world assumptions, such that it can only answer questions and provide results that I should know myself.

In this sense it’s another take on “second brain” tools, but to me it’s potentially a novel angle, using search with closed-world restrictions (ie. much fewer documents, personally stored and indexed) and a question-answering focused interface.

Most other tools focus on the authoring side of things, but I want something that will superpower my memory.

It’s all closed source until I get it going well, but I’ve set up http://rememex.org.