diff --git a/lib/shared/messages/add-members-message-spec.js b/lib/shared/messages/add-members-message-spec.js
--- a/lib/shared/messages/add-members-message-spec.js
+++ b/lib/shared/messages/add-members-message-spec.js
@@ -15,6 +15,11 @@
 import type { NotifTexts } from '../../types/notif-types';
 import type { ThreadInfo } from '../../types/thread-types';
 import type { RelativeUserInfo } from '../../types/user-types';
+import {
+  ET,
+  type EntityText,
+  pluralizeEntityText,
+} from '../../utils/entity-text';
 import { values } from '../../utils/objects';
 import {
   robotextForMessageInfo,
@@ -26,7 +31,6 @@
   MessageSpec,
   MessageTitleParam,
   NotificationTextsParams,
-  RobotextParams,
 } from './message-spec';
 import { joinResult } from './utils';
 
@@ -122,15 +126,16 @@
     return { ...messageData, id };
   },
 
-  robotext(
-    messageInfo: AddMembersMessageInfo,
-    creator: string,
-    params: RobotextParams,
-  ): string {
+  robotext(messageInfo: AddMembersMessageInfo): EntityText {
     const users = messageInfo.addedMembers;
     invariant(users.length !== 0, 'added who??');
-    const addedUsersString = params.robotextForUsers(users);
-    return `${creator} added ${addedUsersString}`;
+
+    const creator = ET.user({ userInfo: messageInfo.creator });
+    const addedUsers = pluralizeEntityText(
+      users.map(user => ET`${ET.user({ userInfo: user })}`),
+    );
+
+    return ET`${creator} added ${addedUsers}`;
   },
 
   notificationTexts(
diff --git a/lib/utils/entity-text.js b/lib/utils/entity-text.js
--- a/lib/utils/entity-text.js
+++ b/lib/utils/entity-text.js
@@ -11,6 +11,7 @@
   type RawThreadInfo,
   type ThreadInfo,
 } from '../types/thread-types';
+import { basePluralize } from '../utils/text-utils';
 
 type UserEntity = {
   +type: 'user',
@@ -288,4 +289,17 @@
   });
 }
 
-export { ET, entityTextToRawString, entityTextToReact };
+function pluralizeEntityText(
+  nouns: $ReadOnlyArray<EntityText>,
+  maxNumberOfNouns: number = 3,
+): EntityText {
+  return basePluralize<EntityText>(
+    nouns,
+    maxNumberOfNouns,
+    [],
+    (a: EntityText | string, b: ?EntityText | string) =>
+      b ? ET`${a}${b}` : ET`${a}`,
+  );
+}
+
+export { ET, entityTextToRawString, entityTextToReact, pluralizeEntityText };