Start with the page, not the test
Google describes structured data as a way to help search systems understand page content. Its quality guidelines require markup to represent that content accurately and warn against misleading information, fake reviews and irrelevant material. A syntactically valid object can still be wrong.
That makes the usual fill-every-field approach risky. A startup directory may know a product's name, website and category without knowing its current price. Putting zero in an offer field does not mean the data is complete. It means the page is asserting a free price, which may be false.
Only mark up what you can support
Use a type that fits the actual page. An article should describe its article, and a list should describe the items visibly listed. Keep titles, dates and images consistent with what readers see. Google says image properties should be relevant and accessible for crawling.
Ratings deserve particular care. A directory vote counter is not automatically a star review, and an editorial impression is not a body of customer ratings. Do not manufacture a rating count or average to make the result more attractive. If you lack the required evidence, leave the unsupported claim out.
Understand the consequence of missing data
Omitting a required property may mean the page is not eligible for a particular rich-result feature. Google's guidelines are clear that required properties matter. That does not justify inventing the property. Prefer an accurate simpler description over a richer-looking object that misstates the offer.
Also separate a test result from a search outcome. Google explicitly says correct markup does not guarantee that a rich result will appear. Display depends on other factors, including the query and broader search context. No plugin or schema template can honestly promise a special appearance for every page.
Make markup part of maintenance
When a page changes, review its structured data with the content. A discontinued offer, renamed product or replacement image can leave stale metadata behind even when the visible page is updated. Generate values from the same maintained record where possible, then inspect representative outputs.
Use validation tools for technical errors and a human check for meaning. Ask a simple question: if a visitor read this markup as a plain sentence, would it be true and supported by the page? If the answer is uncertain, narrow the claim before publishing it.