diff --git a/plivo/resources/multipartycall.py b/plivo/resources/multipartycall.py
index e6c80eab..77fbdef3 100644
--- a/plivo/resources/multipartycall.py
+++ b/plivo/resources/multipartycall.py
@@ -295,6 +295,10 @@ def add_participant(self,
             raise ValidationError('specify either call_uuid or (from, to)')
         if call_uuid is None and (not from_ or not to_):
             raise ValidationError('specify (from, to) when not adding an existing call_uuid to multi party participant')
+        if len(to_.split('<')) > 1 and role.lower() != "agent":
+            raise ValidationError('Multiple to_  values given for role ' + role)
+        elif len(to_.split('<')) > 20:
+            raise ValidationError('No of to_ values provided should be lesser than 20')
         return self.client.request('POST', ('MultiPartyCall', mpc_id, 'Participant'),
                                    self.__clean_identifiers(to_param_dict(self.add_participant, locals())),
                                    is_voice_request=True)