diff --git a/lib/extract_entity.xsl b/lib/extract_entity.xsl
index 6a25135..b305f21 100644
--- a/lib/extract_entity.xsl
+++ b/lib/extract_entity.xsl
@@ -18,9 +18,11 @@
 	extract_entity.xsl
 	
 	An XSL transform that takes a SAML V2.0 metadata file and 
-	a stringparam (entityID) on the command line. It then 
-	extracts the entity descriptor with the given entityID
-	from the aggregate.
+	a stringparam (entityID) on the command line. The metadata
+	file is assumed to be an aggregate of entities, that is, 
+	the root element is the md:EntitiesDescriptor element.
+	The scripts then extracts the entity descriptor with the 
+	given entityID from the aggregate.
 	
 	See md_tools.sh for a use of this stylesheet.
 -->