Clarity — is the product stated plainly, early, in words outside the company's own vocabulary?
Specificity — concrete claims versus unfalsifiable ones. "Cuts onboarding to two days" beats "drives transformation."
Jargon — density of terms that carry no information for a buyer. Higher score means less jargon.
Proof — numbers, named customers, demos. Anything a sceptic could verify.
CTA — does the next step follow from what was just promised?
Not a judgement of the product, the company, or the people. Plenty of excellent products have incoherent homepages, and some of the clearest pages belong to mediocre tools. The index measures communication, nothing else.
Rescored on request when a page changes. Scores are never edited by hand and never altered for payment — the record of every change lives in a public git repository.