diff --git a/uwb/aidl/android/hardware/uwb/fira_android/UwbVendorGidAndroidOids.aidl b/uwb/aidl/android/hardware/uwb/fira_android/UwbVendorGidAndroidOids.aidl
index 42d52f1..4768f55 100644
--- a/uwb/aidl/android/hardware/uwb/fira_android/UwbVendorGidAndroidOids.aidl
+++ b/uwb/aidl/android/hardware/uwb/fira_android/UwbVendorGidAndroidOids.aidl
@@ -30,6 +30,8 @@
     ANDROID_GET_POWER_STATS = 0x0,
     // Used to set the current regulatory country code (determined usinag
     // SIM or hardcoded by OEM).
+    // Country code is sent as a 2 byte value corresponding to ISO-3166 country code.
+    // Note: "00" is used to indicate that the country code is unknown.
     ANDROID_SET_COUNTRY_CODE = 0x1,
     // Used by the notification to get UWB ranging diagnostics stats.
     // Supported only if the UwbVendorCapabilityTlvTypes.SUPPORTED_DIAGNOSTICS set