docs: improve Doxygen comments.

refs: #1435

Change-Id: I21624ef4eec393c82a50229a07e8277fb6ae4ddf
diff --git a/src/name-prefix-list.hpp b/src/name-prefix-list.hpp
index 02445af..a4e71f0 100644
--- a/src/name-prefix-list.hpp
+++ b/src/name-prefix-list.hpp
@@ -37,14 +37,16 @@
 
   ~NamePrefixList();
 
-  /** \brief inserts name into NamePrefixList
-   *  \return true if the name is inserted, otherwise false
+  /*! \brief inserts name into NamePrefixList
+      \retval true If the name was successfully inserted.
+      \retval false If the name could not be inserted.
    */
   bool
   insert(const ndn::Name& name);
 
-  /** \brief removes name from NamePrefixList
-   *  \return true if the name is removed, otherwise false
+  /*! \brief removes name from NamePrefixList
+      \retval true If the name is removed
+      \retval false If the name failed to be removed.
    */
   bool
   remove(const ndn::Name& name);