Use constant

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/AtAll.kt

@@ -38,7 +38,7 @@ object AtAll :
 
     @Suppress("SpellCheckingInspection")
     override fun toString(): String = "[mirai:atall]"
-    override fun contentToString(): String = "@全体成员"
+    override fun contentToString(): String = display
 
     // 自动为消息补充 " "