Research depth
Discovery
How well the tool supports keyword, competitor, SERP, backlink, or market research before execution.
Copywritely
Moderate content-oriented research depth.
The SERP checker accepts up to three keywords, supports several engines/languages, and analyzes selected competitor pages for common words, bigrams and trigrams. https://copywritely.com/serp-checker/
Kafkai
Useful focused competitor and topic-level intelligence, but not positioned as a massive all-purpose SEO database.
Kafkai lists Market X-Ray Vision, Topic-Level Market Map, competitor ranking overview, and content-gap analysis. https://kafkai.com/en/features/