diff --git a/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/Activity.kt b/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/Activity.kt
deleted file mode 100644
index 8db40e2f..00000000
--- a/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/Activity.kt
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * GitMessengerBot © 2021 지성빈 & 구환. all rights reserved.
- * GitMessengerBot license is under the GPL-3.0.
- *
- * [Activity.kt] created by Ji Sungbin on 21. 8. 30. 오후 5:05
- *
- * Please see: https://github.com/GitMessengerBot/GitMessengerBot-Android/blob/master/LICENSE.
- */
-
-package io.github.jisungbin.gitmessengerbot.common.extension
-
-import android.app.Activity
-import android.widget.Toast
-
-fun Activity.toast(message: String, length: Int = Toast.LENGTH_SHORT) {
-    toast(this, message, length)
-}
diff --git a/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/UI.kt b/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/toast.kt
similarity index 71%
rename from common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/UI.kt
rename to common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/toast.kt
index adc70b76..f9b2b888 100644
--- a/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/UI.kt
+++ b/common/src/main/kotlin/io/github/jisungbin/gitmessengerbot/common/extension/toast.kt
@@ -2,7 +2,7 @@
  * GitMessengerBot © 2021 지성빈 & 구환. all rights reserved.
  * GitMessengerBot license is under the GPL-3.0.
  *
- * [UI.kt] created by Ji Sungbin on 21. 8. 30. 오후 5:06
+ * [toast.kt] created by Ji Sungbin on 21. 8. 30. 오후 5:06
  *
  * Please see: https://github.com/GitMessengerBot/GitMessengerBot-Android/blob/master/LICENSE.
  */
@@ -13,9 +13,9 @@ import android.app.Activity
 import android.content.Context
 import android.widget.Toast
 
-fun toast(activity: Activity, message: String, length: Int = Toast.LENGTH_SHORT) {
-    activity.runOnUiThread {
-        toast(activity, message, length)
+fun Activity.toast(message: String, length: Int = Toast.LENGTH_SHORT) {
+    runOnUiThread {
+        toast(this, message, length)
     }
 }
 
diff --git a/core/src/main/kotlin/io/github/sungbin/gitmessengerbot/core/bot/api/UI.kt b/core/src/main/kotlin/io/github/sungbin/gitmessengerbot/core/bot/api/UI.kt
index d2030bce..d74cdacb 100644
--- a/core/src/main/kotlin/io/github/sungbin/gitmessengerbot/core/bot/api/UI.kt
+++ b/core/src/main/kotlin/io/github/sungbin/gitmessengerbot/core/bot/api/UI.kt
@@ -2,7 +2,7 @@
  * GitMessengerBot © 2021 지성빈 & 구환. all rights reserved.
  * GitMessengerBot license is under the GPL-3.0.
  *
- * [UI.kt] created by Ji Sungbin on 21. 7. 10. 오전 11:35.
+ * [toast.kt] created by Ji Sungbin on 21. 7. 10. 오전 11:35.
  *
  * Please see: https://github.com/GitMessengerBot/GitMessengerBot-Android/blob/master/LICENSE.
  */