diff --git a/build/Android.mk b/build/Android.mk
index 220fee77d..8e361e982 100644
--- a/build/Android.mk
+++ b/build/Android.mk
@@ -101,6 +101,9 @@ ALL_SDK_FILES += $(TARGET_OUT_COMMON_INTERMEDIATES)/JAVA_LIBRARIES/android_uiaut
 # org.apache.http.legacy.jar stubs
 ALL_SDK_FILES += $(TARGET_OUT_COMMON_INTERMEDIATES)/JAVA_LIBRARIES/org.apache.http.legacy.stubs_intermediates/classes.jar
 
+# Android Automotive OS stubs
+ALL_SDK_FILES += $(OUT_DIR)/target/common/obj/JAVA_LIBRARIES/android.car-stubs_intermediates/classes.jar
+
 # test stubs
 ALL_SDK_FILES += $(TARGET_OUT_COMMON_INTERMEDIATES)/JAVA_LIBRARIES/android.test.mock.stubs_intermediates/classes.jar
 ALL_SDK_FILES += $(TARGET_OUT_COMMON_INTERMEDIATES)/JAVA_LIBRARIES/android.test.base.stubs_intermediates/classes.jar
diff --git a/build/README.md b/build/README.md
new file mode 100644
index 000000000..8bb2df451
--- /dev/null
+++ b/build/README.md
@@ -0,0 +1,11 @@
+# Android SDK
+
+This directory contains configuration for building Android SDK. The root
+configuration file is `sdk.atree`.
+
+## Building the SDK
+
+```
+$ lunch sdk
+$ m -j sdk
+```
diff --git a/build/sdk.atree b/build/sdk.atree
index 41b746a4b..8fb30d53d 100644
--- a/build/sdk.atree
+++ b/build/sdk.atree
@@ -17,11 +17,6 @@
 #
 # These are the files that comprise that SDK.
 #
-# The files that will go in the tools folder are setup through
-#    sdk/build/tools.atree
-# This is to help when the sdk.git project is branched differently from
-# the other projects.
-#
 
 ##############################################################################
 # SDK Root folder
@@ -170,10 +165,10 @@ ${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/core-current-stubs-for-system-module
 # optional API files.
 development/build/optional.json                                                               platforms/${PLATFORM_NAME}/optional/optional.json
 ${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/org.apache.http.legacy.stubs_intermediates/classes.jar  platforms/${PLATFORM_NAME}/optional/org.apache.http.legacy.jar
-# Android Automotive OS stubs.
-prebuilts/sdk/29/public/android.car.jar                                                       platforms/${PLATFORM_NAME}/optional/android.car.jar
 # deprecated APIs
 ${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/android_uiautomator_intermediates/classes.jar     platforms/${PLATFORM_NAME}/uiautomator.jar
+# Android Automotive OS stubs.
+${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/android.car-stubs_intermediates/classes.jar         platforms/${PLATFORM_NAME}/optional/android.car.jar
 # Test APIs
 ${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/android.test.mock.stubs_intermediates/classes.jar   platforms/${PLATFORM_NAME}/optional/android.test.mock.jar
 ${OUT_DIR}/target/common/obj/JAVA_LIBRARIES/android.test.base.stubs_intermediates/classes.jar   platforms/${PLATFORM_NAME}/optional/android.test.base.jar