Five rules
- One fact, one sentence. "The 45-litre version holds a 15-inch laptop in
a separate sleeve." Not a list of adjectives.
- Units always. "45 litres", not "45". "Weighs 1.2 kg", not "lightweight".
- The variant it applies to. Facts that differ between variants are stated
per variant.
- The limit. "Fits carry-on limits on most European airlines; not the
40 × 20 × 25 cm limit of some low-cost carriers."
- What it does not do. "Does not include the rain cover." A missing
boundary is filled with a guess.
Where to put them
In the HTML the server sends, near the product name — not only in tabs built by scripts, and not only in images. Check with a fetch without JavaScript: /learn/how-to-make-product-facts-readable-without-javascript.
Why sentences
In answers about real products, 44% of citations went to press, review and reference pages (study). Those pages usually state facts in sentences. A product page that does the same gives a model a primary source for the same fact. What that does and does not prove is at /evidence.