diff --git a/doc/design_ros_2.md b/doc/design_ros_2.md
index 668aea2..d2bfa37 100644
--- a/doc/design_ros_2.md
+++ b/doc/design_ros_2.md
@@ -2,6 +2,13 @@
 
 Design document for ROS 2 tracing, instrumentation, and analysis effort.
 
+## Introduction
+
+Tracing allows to record run-time data from a system, both for system data (e.g., when a process
+is being scheduled, or when I/O occurs) and for user-defined data. This package helps with
+user-defined trace data within the ROS2 framework, e.g. to trace when messages arrive,
+when timers fire, when callbacks are being run, etc.
+
 ## Goals and requirements
 
 ### Goals