diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index ab059e18295c1b37b5b31b52df161f482e744773..673eed6201a6a813959aaec12f873e73af62b3b3 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -2300,6 +2300,9 @@ These functions return the leftover itemstack.
     * currently supported.
     * `...` indicates method-specific arguments. Currently, no methods use this.
 * `minetest.is_protected(pos, name)`: returns boolean
+    * Returns true, if player `name` shouldn't be abled to dig at `pos` or do other
+      actions, defineable by mods, due to some mod-defined ownership-like concept.
+      Returns false or nil, if the player is allowed to do such actions.
     * This function should be overridden by protection mods and should be used to
       check if a player can interact at a position.
     * This function should call the old version of itself if the position is not