diff --git a/README.md b/README.md
index 0d956b5..8eccfd3 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,9 @@
 
 This package relies heavily on the [`daily_flutter`](https://pub.dev/packages/daily_flutter) package. Please refer to the [daily_flutter pub.dev page](https://pub.dev/packages/daily_flutter) for the most up-to-date version constraints and platform requirements.
 
+**iOS:** Requires iOS 13.0 or higher due to the `daily_flutter` dependency.
+**Android:** Requires SDK version 24 or higher due to the `daily_flutter` dependency.
+
 ### Web
 
 - No special requirements. The Vapi Web SDK is loaded under the hood via [jsdelivr](https://www.jsdelivr.com/), and a specific version is hardcoded to ensure compatibility with this Flutter package. For more details, see `lib/src/platform/web/vapi_web_client.dart`.
@@ -37,6 +40,12 @@ Then, follow the platform-specific setup instructions for `permission_handler`:
 
 ### iOS
 
+**Important:** This package requires iOS 13.0 or higher due to the `daily_flutter` dependency. Make sure to set the iOS deployment target in your Podfile:
+
+```ruby
+platform :ios, '13.0'
+```
+
 According to the permission_handler instructions above, add the permission flags for microphone.
 
 Also add this to your Info.plist:
@@ -77,6 +86,16 @@ Add the necessary permissions to your AndroidManifest.xml:
 
 Add the permission flags for microphone according to the permission_handler instructions above.
 
+**Important:** This package requires Android SDK version 24 or higher due to the `daily_flutter` dependency. Make sure to set the minimum SDK version in your build.gradle.kts:
+
+```kotlin
+android {
+    defaultConfig {
+        minSdk = 24
+    }
+}
+```
+
 ---
 
 ### Web
diff --git a/lib/src/platform/mobile/vapi_mobile_call.dart b/lib/src/platform/mobile/vapi_mobile_call.dart
index c661851..c4eb0f1 100644
--- a/lib/src/platform/mobile/vapi_mobile_call.dart
+++ b/lib/src/platform/mobile/vapi_mobile_call.dart
@@ -119,8 +119,9 @@ class VapiMobileCall implements VapiCall {
   final String webCallUrl;
 
   /// ID of the assistant handling this call
+  /// May be null when using inline assistant configuration
   @override
-  final String assistantId;
+  final String? assistantId;
 
   /// Assistant configuration overrides for this call
   @override
@@ -165,7 +166,7 @@ class VapiMobileCall implements VapiCall {
     final transport = VapiCallTransport.fromJson(
         apiResponse['transport'] as Map<String, dynamic>);
     final webCallUrl = apiResponse['webCallUrl'] as String;
-    final assistantId = apiResponse['assistantId'] as String;
+    final assistantId = apiResponse['assistantId'] as String?;
     final assistantOverrides = Map<String, dynamic>.from(
         apiResponse['assistantOverrides'] as Map<String, dynamic>);
 
diff --git a/lib/src/platform/web/vapi_web_call.dart b/lib/src/platform/web/vapi_web_call.dart
index 18a3756..156788d 100644
--- a/lib/src/platform/web/vapi_web_call.dart
+++ b/lib/src/platform/web/vapi_web_call.dart
@@ -83,8 +83,9 @@ class VapiWebCall implements VapiCall {
   final String webCallUrl;
 
   /// ID of the assistant handling this call.
+  /// May be null when using inline assistant configuration.
   @override
-  final String assistantId;
+  final String? assistantId;
 
   /// Assistant configuration overrides for this call.
   @override
@@ -156,7 +157,7 @@ class VapiWebCall implements VapiCall {
     final transportTmp = Map<String, dynamic>.from(callData['transport']);
     final transport = VapiCallTransport.fromJson(transportTmp);
     final webCallUrl = callData['webCallUrl'];
-    final assistantId = callData['assistantId'];
+    final assistantId = callData['assistantId'] as String?;
     final assistantOverrides =
         Map<String, dynamic>.from(callData['assistantOverrides']);
 
diff --git a/lib/src/vapi_call_interface.dart b/lib/src/vapi_call_interface.dart
index 3b448a4..d874328 100644
--- a/lib/src/vapi_call_interface.dart
+++ b/lib/src/vapi_call_interface.dart
@@ -19,7 +19,8 @@ abstract interface class VapiCall {
   String get id;
 
   /// ID of the assistant handling this call.
-  String get assistantId;
+  /// May be null when using inline assistant configuration.
+  String? get assistantId;
 
   /// Assistant configuration overrides for this call.
   Map<String, dynamic> get assistantOverrides;