The product
What the Grok research paper checker reports
Paste a section of academic prose and the checker returns a description of what is observable in it: the distribution of sentence lengths, connective phrasing characteristic of generated text, vocabulary held inside a narrow range, and claims asserted without the particulars that would evidence them. The framing is academic writing specifically, and drafts that passed through Grok in particular.
It runs remotely. The section is sent to our server, read once by a language model, and the description returns to the page. 5 free runs in any rolling 24 hours, 1 to 12,000 characters per run, nothing retained afterward.
It returns no probability. That is a design decision rather than a missing feature, and the rest of this page is largely an argument for it.