What this tool checks
Fetches /sitemap.xml at the domain root, detects whether it's a regular sitemap (<urlset>, listing page URLs directly) or a sitemap index (<sitemapindex>, listing other sitemap files — used by larger sites split across multiple sitemap files), counts the total number of <loc> entries, and spot-checks a representative sample of 10 of them for whether they still respond with a working status.
Why "found: false" isn't necessarily bad
Not every site needs a sitemap to be well-indexed — a small site with a clear internal link structure can be fully discovered by search engines without one. A missing sitemap is a signal worth knowing about, especially for larger or frequently-changing sites where it meaningfully speeds up discovery of new content, but it isn't itself a broken state.
Why the sample is spread evenly, not just the first 10
Sitemaps are often generated in a stable order (e.g., oldest content first, or alphabetically) — checking only the first 10 entries would systematically miss problems concentrated later in the list, like a batch of pages from a specific time period that later broke. Spreading the sample across the entire list gives a much more representative signal for the same number of requests.