diff --git a/android/sdk.go b/android/sdk.go
index ad67bbe..32d9921 100644
--- a/android/sdk.go
+++ b/android/sdk.go
@@ -186,9 +186,33 @@
 	// is correctly output for both versioned and unversioned prebuilts in the
 	// snapshot.
 	//
+	// "required: true" means that the property must only contain references
+	// to other members of the sdk. Passing a reference to a module that is not a
+	// member of the sdk will result in a build error.
+	//
+	// "required: false" means that the property can contain references to modules
+	// that are either members or not members of the sdk. If a reference is to a
+	// module that is a non member then the reference is left unchanged, i.e. it
+	// is not transformed as references to members are.
+	//
+	// The handling of the member names is dependent on whether it is an internal or
+	// exported member. An exported member is one whose name is specified in one of
+	// the member type specific properties. An internal member is one that is added
+	// due to being a part of an exported (or other internal) member and is not itself
+	// an exported member.
+	//
+	// Member names are handled as follows:
+	// * When creating the unversioned form of the module the name is left unchecked
+	//   unless the member is internal in which case it is transformed into an sdk
+	//   specific name, i.e. by prefixing with the sdk name.
+	//
+	// * When creating the versioned form of the module the name is transformed into
+	//   a versioned sdk specific name, i.e. by prefixing with the sdk name and
+	//   suffixing with the version.
+	//
 	// e.g.
-	// bpPropertySet.AddPropertyWithTag("libs", []string{"member1", "member2"}, builder.SdkMemberReferencePropertyTag())
-	SdkMemberReferencePropertyTag() BpPropertyTag
+	// bpPropertySet.AddPropertyWithTag("libs", []string{"member1", "member2"}, builder.SdkMemberReferencePropertyTag(true))
+	SdkMemberReferencePropertyTag(required bool) BpPropertyTag
 }
 
 type BpPropertyTag interface{}