diff --git a/src/oatpp/core/async/Coroutine.hpp b/src/oatpp/core/async/Coroutine.hpp
index 8befeaed..4c24dba4 100644
--- a/src/oatpp/core/async/Coroutine.hpp
+++ b/src/oatpp/core/async/Coroutine.hpp
@@ -113,6 +113,9 @@ public:
 
 public:
 
+  /**
+   * Event type qualifier for Actions of type &l:Action::TYPE_IO_WAIT;, &l:Action::TYPE_IO_REPEAT;.
+   */
   enum IOEventType : v_int32 {
     /**
      * IO event type READ.
diff --git a/src/oatpp/core/data/IODefinitions.hpp b/src/oatpp/core/data/IODefinitions.hpp
index cee9bd41..6dc44ee2 100644
--- a/src/oatpp/core/data/IODefinitions.hpp
+++ b/src/oatpp/core/data/IODefinitions.hpp
@@ -56,13 +56,13 @@ typedef v_int64 v_io_size;
 enum IOError : v_io_size {
 
   /**
-   * In oatpp 0 is considered to be an Error as for I/O operation size
+   * In oatpp 0 is considered to be an Error as for I/O operation size. <br>
    *
-   * As for argument value 0 should be handled separately of the main flow.
+   * As for argument value 0 should be handled separately of the main flow.<br>
    *
-   * As for return value 0 should not be returned.
-   * I/O method should return an error describing a reason why I/O is empty instead of a zero itself.
-   * if zero is returned, client should treat it like a bad api implementation and as an error in the flow.
+   * As for return value 0 should not be returned.<br>
+   * I/O method should return an error describing a reason why I/O is empty instead of a zero itself.<br>
+   * if zero is returned, client should treat it like a bad api implementation and as an error in the flow.<br>
    */
   ZERO_VALUE = 0,
 
diff --git a/src/oatpp/core/data/stream/Stream.hpp b/src/oatpp/core/data/stream/Stream.hpp
index 3a293140..d4399b46 100644
--- a/src/oatpp/core/data/stream/Stream.hpp
+++ b/src/oatpp/core/data/stream/Stream.hpp
@@ -32,8 +32,19 @@
 
 namespace oatpp { namespace data{ namespace stream {
 
+/**
+ * Stream I/O mode.
+ */
 enum IOMode : v_int32 {
+
+  /**
+   * Blocking stream I/O mode.
+   */
   BLOCKING = 0,
+
+  /**
+   * Non-blocking stream I/O mode.
+   */
   NON_BLOCKING = 1
 };