diff --git a/CHANGELOG.md b/CHANGELOG.md
index f7cd9eb4ef..d32174f6a4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 ## 21.0.0
 
+* `BehaviourBuilder`:
+  * Add special `val data: BehaviourContextData` into all realizations of `BehaviourContext`
+  * Add `CombinedSubcontextInitialAction` and functions
+`buildSubcontextInitialAction`/`buildSubcontextInitialActionWithSubActions`
+  * Add `subcontextInitialAction` for all the functions-builders of `BehaviourContext` and
+`additionalSubcontextInitialAction` to all triggers
+
 ## 20.0.1
 
 * `Core`:
diff --git a/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/CombinedSubcontextInitialAction.kt b/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/CombinedSubcontextInitialAction.kt
index 5099ba9f00..b4b4ae66a1 100644
--- a/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/CombinedSubcontextInitialAction.kt
+++ b/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/CombinedSubcontextInitialAction.kt
@@ -4,10 +4,17 @@ import dev.inmo.kslog.common.KSLog
 import dev.inmo.kslog.common.error
 import dev.inmo.tgbotapi.types.update.abstracts.Update
 
+/**
+ * Contains [SubAction]s which will be used in [subcontextInitialAction] in order they has been passed in [subactions].
+ */
 class CombinedSubcontextInitialAction(
     val subactions: List<SubAction>,
     private val logger: KSLog = KSLog("CombinedSubcontextInitialAction_${subactions.size}")
 ) {
+    /**
+     * Represents interface-like variant of [CustomBehaviourContextAndTypeReceiver] useful for [BehaviourContext]
+     * builders
+     */
     fun interface SubAction {
         suspend operator fun BehaviourContext.invoke(update: Update)
 
@@ -30,6 +37,10 @@ class CombinedSubcontextInitialAction(
     }
 }
 
+/**
+ * Build [CombinedSubcontextInitialAction] with [block] and return callback, which appropriate for [BehaviourContext]
+ * builders with `subcontextInitialAction` argument
+ */
 inline fun buildSubcontextInitialActionWithSubActions(
     block: MutableList<CombinedSubcontextInitialAction.SubAction>.() -> Unit
 ): CustomBehaviourContextAndTypeReceiver<BehaviourContext, Unit, Update> {
@@ -40,6 +51,10 @@ inline fun buildSubcontextInitialActionWithSubActions(
     ).subcontextInitialAction
 }
 
+/**
+ * Build [CombinedSubcontextInitialAction] with [block] and return callback, which appropriate for [BehaviourContext]
+ * builders with `subcontextInitialAction` argument
+ */
 inline fun buildSubcontextInitialAction(
     block: MutableList<CustomBehaviourContextAndTypeReceiver<BehaviourContext, Unit, Update>>.() -> Unit
 ): CustomBehaviourContextAndTypeReceiver<BehaviourContext, Unit, Update> {