diff --git a/UPGRADE-2.0.md b/UPGRADE-2.0.md
index c4635814d..a2da9c2e2 100644
--- a/UPGRADE-2.0.md
+++ b/UPGRADE-2.0.md
@@ -81,3 +81,5 @@ The providers-api is optional, but if you implement it it should return packages
 This is also optional, it should accept an optional `?filter=xx` query param, which can contain `*` as wildcards matching any substring.
 
 It must return an array of package names as `{"packageNames": ["a/b", "c/d"]}`. See <https://packagist.org/packages/list.json?filter=composer/*> for example.
+
+It should return the names of package which names match the filter (or all names if no filter is present). Replace/provide rules should not be considered here.