A tier says how much evidence sits under a tool. It says nothing about how useful the tool is. A Folklore tool can still be the right one to reach for. It just should not be your answer when someone asks how you know.
Replicated across categories by independent teams. To argue against it you need data, not an opinion.
Not true or false: scaffolding. Its value is forcing a question you would otherwise skip.
Consulting or book-born, widely used, thinly evidenced. Fine as shared language; poor as a basis for a decision.
The tier belongs to the claim the tool makes, not to how famous the tool is. Some of the best known entries here sit in Folklore. That is the finding. It is not an oversight.
Every entry carries one case, and every case links to a source you can open yourself. Where the original exists, we link the original: the paper, the filing, the transcript. A write-up about it comes second. Some entries still rest on a write-up. Those are the ones we are still working on.
A few entries have no independent case at all. We mark them that way instead of filling the gap with a vendor testimonial. An empty column tells you more than a decorative one.
If something here is wrong, tell us. We would rather fix it than defend it.
79 tools across 9 questions. The index is sorted by the question you are stuck on, not by discipline. Nobody turns up looking for a segmentation framework. They turn up not knowing who buys.