What it is
Drop in a CSV and it shows you what is actually in each column: the types, the ranges, the blanks, the seven different spellings of the same city, and the rows that do not have the number of fields the header promised.
What it will not do
Not built yet.
It is listed without a link and will stay that way until it works. There is nothing to sign up to in the meantime — check back, or watch the repository, which is the only place this list is kept.
Why it is listed
It meets all four rules: free to use in full, usable without an account, honest about where the work happens, and clear about what it keeps. The rules are written down, and an app that stops meeting one of them is removed rather than quietly footnoted.
Something here out of date, or wrong? Say so on the issue tracker. The four answers above are the only thing this directory is asking to be believed about, so an entry that has drifted is a bug, not a detail.