diff --git a/src/sdeventplus/source/io.hpp b/src/sdeventplus/source/io.hpp
index 030f75e..f26eac8 100644
--- a/src/sdeventplus/source/io.hpp
+++ b/src/sdeventplus/source/io.hpp
@@ -15,22 +15,82 @@
   public:
     using Callback = std::function<void(IO&, int fd, uint32_t revents)>;
 
+    /** @brief Adds a new IO source handler to the Event
+     *         Executes the callback upon events occurring
+     *
+     *  @param[in] name   - The name identifying the create function
+     *  @param[in] create - The SdEvent function called to create the source
+     *  @param[in] event  - The event to attach the handler
+     *  @param[in] callback - The function executed on event dispatch
+     *  @throws SdEventError for underlying sd_event errors
+     */
     IO(const Event& event, int fd, uint32_t events, Callback&& callback);
 
+    /** @brief Gets the file descriptor tied to the source
+     *
+     *  @throws SdEventError for underlying sd_event errors
+     *  @return The watched file descriptor
+     */
     int get_fd() const;
+
+    /** @brief Sets the file descriptor the source watches
+     *
+     *  @param[in] fd - The file descriptor to watch
+     *  @throws SdEventError for underlying sd_event errors
+     */
     void set_fd(int fd) const;
+
+    /** @brief Gets the events mask used to determine what
+     *         events trigger the callback action
+     *
+     *  @throws SdEventError for underlying sd_event errors
+     *  @return The events mask
+     */
     uint32_t get_events() const;
+
+    /** @brief Sets the events mask used to determine what events
+     *         trigger the callback handler
+     *
+     *  @param[in] events - The events mask
+     *  @throws SdEventError for underlying sd_event errors
+     */
     void set_events(uint32_t events) const;
+
+    /** @brief Gets the events mask describing the events
+     *         seen in the most recent callback
+     *
+     *  @throws SdEventError for underlying sd_event errors
+     *  @return The events mask
+     */
     uint32_t get_revents() const;
 
   private:
     Callback callback;
 
+    /** @brief Returns a reference to the callback executed for this source
+     *
+     *  @return A reference to the callback
+     */
     const Callback& get_callback() const;
 
+    /** @brief Creates a new IO source attached to the Event
+     *
+     *  @param[in] event  - The event to attach the handler
+     *  @param[in] fd     - The file descriptor producing the events
+     *  @param[in] events - The event mask passed which determines triggers
+     *                      See epoll_ctl(2) for more info on the mask
+     *  @throws SdEventError for underlying sd_event errors
+     *  @return A new sd_event_source
+     */
     static sd_event_source* create_source(const Event& event, int fd,
                                           uint32_t events);
 
+    /** @brief A wrapper around the callback that can be called from sd-event
+     *
+     *  @param[in] source   - The sd_event_source associated with the call
+     *  @param[in] userdata - The provided userdata for the source
+     *  @return 0 on success or a negative errno otherwise
+     */
     static int ioCallback(sd_event_source* source, int fd, uint32_t revents,
                           void* userdata);
 };