Improve documentation of EditorPlugin.add_tool_submenu_item method

doc/classes/EditorPlugin.xml

@@ -128,7 +128,7 @@
 			<argument index="3" name="ud" type="Variant" default="null">
 			</argument>
 			<description>
-				Adds a custom menu to [b]Project &gt; Tools[/b] as [code]name[/code] that calls [code]callback[/code] on an instance of [code]handler[/code] with a parameter [code]ud[/code] when user activates it.
+				Adds a custom menu item to [b]Project &gt; Tools[/b] as [code]name[/code] that calls [code]callback[/code] on an instance of [code]handler[/code] with a parameter [code]ud[/code] when user activates it.
 			</description>
 		</method>
 		<method name="add_tool_submenu_item">
@@ -139,7 +139,7 @@
 			<argument index="1" name="submenu" type="Object">
 			</argument>
 			<description>
-				Like [method add_tool_menu_item] but adds the [code]submenu[/code] item inside the [code]name[/code] menu.
+				Adds a custom submenu under [b]Project &gt; Tools &gt;[/b] [code]name[/code]. [code]submenu[/code] should be an object of class [PopupMenu]. This submenu should be cleaned up using [code]remove_tool_menu_item(name)[/code].
 			</description>
 		</method>
 		<method name="apply_changes" qualifiers="virtual">