diff --git a/graphics/allocator/3.0/IAllocator.hal b/graphics/allocator/3.0/IAllocator.hal
index 3651e91..34b08e7 100644
--- a/graphics/allocator/3.0/IAllocator.hal
+++ b/graphics/allocator/3.0/IAllocator.hal
@@ -30,6 +30,9 @@
     /**
      * Allocates buffers with the properties specified by the descriptor.
      *
+     * Allocations should be optimized for usage bits provided in the
+     * descriptor.
+     *
      * @param descriptor Properties of the buffers to allocate. This must be
      *     obtained from IMapper::createDescriptor().
      * @param count The number of buffers to allocate.