GET /api/alpha/search now uses the same full-text search engine as the web UI so you can sort results by relevance. e.g.
https://piefed.crust.social/api/alpha/search?q=test&type_=Posts&sort=Relevance
Also if the q parameter has a value then read posts are included in the results regardless of what the user’s setting is for hiding read posts. That is to avoid this problem: https://piefed.social/c/lemmyconnect/p/1502152/is-there-any-way-to-include-read-posts-in-search-results