diff --git a/java/com/google/gerrit/common/data/PermissionRange.java b/java/com/google/gerrit/common/data/PermissionRange.java
index 8876c02..6b66b33 100644
--- a/java/com/google/gerrit/common/data/PermissionRange.java
+++ b/java/com/google/gerrit/common/data/PermissionRange.java
@@ -17,6 +17,10 @@
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * Represents a closed interval [min, max] with a name. The special value [0, 0] is understood to be
+ * the empty range.
+ */
 public class PermissionRange implements Comparable<PermissionRange> {
   public static class WithDefaults extends PermissionRange {
     protected int defaultMin;