diff --git a/Development_Contribution.md b/Development_Contribution.md
index ed990f9..bcc14dd 100644
--- a/Development_Contribution.md
+++ b/Development_Contribution.md
@@ -76,6 +76,19 @@ class NotifyFooBar(NotifyBase):
         # otherwise return False if it failed.
         return True
 
+    @property
+    def url_identifier(self):
+        """
+        Returns a unique identifier for this plugin instance.
+        This is used to uniquely identify this service from another when
+        generating a unique identifier for the persistent storage engine.
+
+        The goal is to return anything unique to this object (in a tuple)
+        If you have tokens and/or keys derived from the Apprise URL,
+        then you would want to include those items as well in this response.
+        """
+        return (self.protocol, self.host)
+
     def __len__(self):
         """
         Returns the number of targets associated with this notification