Why a screenshot may leave out product information
Screenshots of a product page are useful and lossy. Knowing what they drop tells you what to add alongside.
Sharing a product page as a screenshot is quick and it is what most people do. It is also lossy in ways that are invisible to the person taking it, because the things it drops are precisely the things that were off-screen or not rendered as pixels.
This is not an argument against screenshots. It is a short list of what to send with one.
What the picture leaves behind
The address - A screenshot does not carry the page it came from. Paste the full address as text as well. It is the only part of the message that lets somebody check the current state of the page.
Anything below the fold - Specification tables are often longer than the visible window. A screenshot of the top of a table looks complete and is not.
Rows that read as awaiting confirmation - These matter more than the rows with values, and they are easy to crop out because they look like less important text.
The date you looked - Pages get updated. A screenshot with no date cannot be compared against the current page.
Which model you were on - Family pages and model pages look similar. If the screenshot is cropped to a table, the designation may not be in the image at all.
The pattern that works
So the pattern that works is simple: send the address as text, then the screenshot, then one sentence saying what you want the recipient to look at. The address makes it checkable, the screenshot makes it fast, and the sentence stops the reply answering a different question.
If you are sharing several pages, keep them as separate address-plus-image pairs rather than one long strip of images. A strip of five screenshots is answered as one question, which is rarely what was wanted.
When you are reporting a difference
One special case. If you are screenshotting to report that something looks wrong - a value you did not expect, a row that contradicts a document you hold - say what you expected as well as what you saw. "This says Φ4mm, our drawing says Φ6mm" is a question that can be investigated. A screenshot with "is this right?" underneath is not.
Address as text, screenshot, and one sentence on what you want checked.