diff --git a/README.md b/README.md
index 365d995..c330d9c 100644
--- a/README.md
+++ b/README.md
@@ -39,6 +39,14 @@ Queries that share no vocabulary with the package data (gibberish,
 keyboard mash) return an honest empty result instead of random
 semantic matches.
 
+**Why is this package in my results?** Each result knows which search
+strategy produced it. The controller exposes this as
+`@search_sources` (a hash mapping package ids to `:exact`,
+`:name_prefix`, `:name_contains`, `:semantic` or `:fulltext`). For
+debugging you can render a small badge on every result card by adding
+`show_sources=1` to the URL, e.g.
+`https://screenshots.debian.net/packages?search=sqlite&show_sources=1`.
+
 Package pages also show semantically **related packages**, computed as
 a nearest neighbor query against the package's own description
 embedding - no external service call involved.