diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaController.java b/libraries/session/src/main/java/androidx/media3/session/MediaController.java
index 529be85dcc..44acda8293 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaController.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaController.java
@@ -905,13 +905,14 @@ public class MediaController implements Player {
   /**
    * Sends a custom command to the session.
    *
+   * <p>A command is not accepted if it is not a custom command or the command is not in the list of
+   * {@linkplain #getAvailableSessionCommands() available session commands}.
+   *
    * <p>Interoperability: When connected to {@link
    * android.support.v4.media.session.MediaSessionCompat}, {@link SessionResult#resultCode} will
    * return the custom result code from the {@code android.os.ResultReceiver#onReceiveResult(int,
    * Bundle)} instead of the standard result codes defined in the {@link SessionResult}.
    *
-   * <p>A command is not accepted if it is not a custom command.
-   *
    * @param command The custom command.
    * @param args The additional arguments. May be empty.
    * @return A {@link ListenableFuture} of {@link SessionResult} representing the pending
diff --git a/libraries/session/src/main/java/androidx/media3/session/MediaSession.java b/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
index 601920bbdc..3c82ec75d2 100644
--- a/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
+++ b/libraries/session/src/main/java/androidx/media3/session/MediaSession.java
@@ -1042,6 +1042,10 @@ public class MediaSession {
      * Called when a controller sent a custom command through {@link
      * MediaController#sendCustomCommand(SessionCommand, Bundle)}.
      *
+     * <p>{@link MediaController} instances are only allowed to send a command if the command has
+     * been added to the {@link MediaSession.ConnectionResult#availableSessionCommands list of
+     * available session commands} in {@link #onConnect} or set via {@link #setAvailableCommands}.
+     *
      * <p>Interoperability: This will be also called by {@link
      * android.support.v4.media.MediaBrowserCompat#sendCustomAction}. If so, {@code extras} from
      * {@link android.support.v4.media.MediaBrowserCompat#sendCustomAction} will be considered as