diff --git a/rclcpp/include/rclcpp/client.hpp b/rclcpp/include/rclcpp/client.hpp
index f7f1d5cb8c..e6b02f9969 100644
--- a/rclcpp/include/rclcpp/client.hpp
+++ b/rclcpp/include/rclcpp/client.hpp
@@ -84,22 +84,42 @@ class ClientBase
   bool
   take_type_erased_response(void * response_out, rmw_request_id_t & request_header_out);
 
+  /// Return the name of the service.
+  /** \return The name of the service. */
   RCLCPP_PUBLIC
   const char *
   get_service_name() const;
 
+  /// Return the rcl_client_t client handle in a std::shared_ptr.
+  /**
+   * This handle remains valid after the Client is destroyed.
+   * The actual rcl client is not finalized until it is out of scope everywhere.
+   */
   RCLCPP_PUBLIC
   std::shared_ptr<rcl_client_t>
   get_client_handle();
 
+  /// Return the rcl_client_t client handle in a std::shared_ptr.
+  /**
+   * This handle remains valid after the Client is destroyed.
+   * The actual rcl client is not finalized until it is out of scope everywhere.
+   */
   RCLCPP_PUBLIC
   std::shared_ptr<const rcl_client_t>
   get_client_handle() const;
 
+  /// Return if the service is ready.
+  /**
+   * \return `true` if the service is ready, `false` otherwise
+   */
   RCLCPP_PUBLIC
   bool
   service_is_ready() const;
 
+  /// Wait for a service to be ready.
+  /**
+   * \param timeout maximum time to wait
+   */
   template<typename RepT = int64_t, typename RatioT = std::milli>
   bool
   wait_for_service(
diff --git a/rclcpp/include/rclcpp/clock.hpp b/rclcpp/include/rclcpp/clock.hpp
index 3b5b22515a..211966ee41 100644
--- a/rclcpp/include/rclcpp/clock.hpp
+++ b/rclcpp/include/rclcpp/clock.hpp
@@ -89,6 +89,7 @@ class Clock
   bool
   ros_time_is_active();
 
+  /// Return the rcl_clock_t clock handle
   RCLCPP_PUBLIC
   rcl_clock_t *
   get_clock_handle() noexcept;
@@ -97,6 +98,7 @@ class Clock
   rcl_clock_type_t
   get_clock_type() const noexcept;
 
+  /// Get the clock's mutex
   RCLCPP_PUBLIC
   std::mutex &
   get_clock_mutex() noexcept;
diff --git a/rclcpp/include/rclcpp/duration.hpp b/rclcpp/include/rclcpp/duration.hpp
index 5e09cc5cb1..eb716c3348 100644
--- a/rclcpp/include/rclcpp/duration.hpp
+++ b/rclcpp/include/rclcpp/duration.hpp
@@ -26,11 +26,22 @@ namespace rclcpp
 class RCLCPP_PUBLIC Duration
 {
 public:
+  /// Duration constructor.
+  /**
+   * Initializes the time values for seconds and nanoseconds individually.
+   * Large values for nsecs are wrapped automatically with the remainder added to secs.
+   * Both inputs must be integers.
+   * Seconds can be negative.
+   *
+   * \param seconds time in seconds
+   * \param nanoseconds time in nanoseconds
+   */
   Duration(int32_t seconds, uint32_t nanoseconds);
 
-  // This constructor matches any numeric value - ints or floats
+  // This constructor matches any numeric value - ints or floats.
   explicit Duration(rcl_duration_value_t nanoseconds);
 
+  // This constructor matches std::chrono::nanoseconds.
   explicit Duration(std::chrono::nanoseconds nanoseconds);
 
   // This constructor matches any std::chrono value other than nanoseconds
@@ -44,6 +55,10 @@ class RCLCPP_PUBLIC Duration
   // cppcheck-suppress noExplicitConstructor
   Duration(const builtin_interfaces::msg::Duration & duration_msg);  // NOLINT(runtime/explicit)
 
+  /// Time constructor
+  /**
+   * \param duration rcl_duration_t structure to copy.
+   */
   explicit Duration(const rcl_duration_t & duration);
 
   Duration(const Duration & rhs);
@@ -80,6 +95,10 @@ class RCLCPP_PUBLIC Duration
   Duration
   operator-(const rclcpp::Duration & rhs) const;
 
+  /// Get the maximum representable value.
+  /**
+   * \return the maximum representable value
+   */
   static
   Duration
   max();
@@ -87,19 +106,27 @@ class RCLCPP_PUBLIC Duration
   Duration
   operator*(double scale) const;
 
+  /// Get duration in nanosecods
+  /**
+   * \return the duration in nanoseconds as a rcl_duration_value_t.
+   */
   rcl_duration_value_t
   nanoseconds() const;
 
-  /// \return the duration in seconds as a floating point number.
-  /// \warning Depending on sizeof(double) there could be significant precision loss.
-  /// When an exact time is required use nanoseconds() instead.
+  /// Get duration in seconds
+  /**
+   * \warning Depending on sizeof(double) there could be significant precision loss.
+   *   When an exact time is required use nanoseconds() instead.
+   * \return the duration in seconds as a floating point number.
+   */
   double
   seconds() const;
 
-  // Create a duration object from a floating point number representing seconds
+  /// Create a duration object from a floating point number representing seconds
   static Duration
   from_seconds(double seconds);
 
+  /// Convert Duration into a std::chrono::Duration.
   template<class DurationT>
   DurationT
   to_chrono() const
@@ -107,6 +134,7 @@ class RCLCPP_PUBLIC Duration
     return std::chrono::duration_cast<DurationT>(std::chrono::nanoseconds(this->nanoseconds()));
   }
 
+  /// Convert Duration into rmw_time_t.
   rmw_time_t
   to_rmw_time() const;
 
diff --git a/rclcpp/include/rclcpp/node.hpp b/rclcpp/include/rclcpp/node.hpp
index 6131fef95a..7279a6a97e 100644
--- a/rclcpp/include/rclcpp/node.hpp
+++ b/rclcpp/include/rclcpp/node.hpp
@@ -186,8 +186,8 @@ class Node : public std::enable_shared_from_this<Node>
   /// Create and return a Subscription.
   /**
    * \param[in] topic_name The topic to subscribe on.
+   * \param[in] qos QoS profile for Subcription.
    * \param[in] callback The user-defined callback function to receive a message
-   * \param[in] qos_history_depth The depth of the subscription's incoming message queue.
    * \param[in] options Additional options for the creation of the Subscription.
    * \param[in] msg_mem_strat The message memory strategy to use for allocating messages.
    * \return Shared pointer to the created subscription.
@@ -229,7 +229,13 @@ class Node : public std::enable_shared_from_this<Node>
     CallbackT callback,
     rclcpp::CallbackGroup::SharedPtr group = nullptr);
 
-  /* Create and return a Client. */
+  /// Create and return a Client.
+  /**
+   * \param[in] service_name The topic to service on.
+   * \param[in] rmw_qos_profile_t Quality of service profile for client.
+   * \param[in] group Callback group to call the service.
+   * \return Shared pointer to the created client.
+   */
   template<typename ServiceT>
   typename rclcpp::Client<ServiceT>::SharedPtr
   create_client(
@@ -237,7 +243,14 @@ class Node : public std::enable_shared_from_this<Node>
     const rmw_qos_profile_t & qos_profile = rmw_qos_profile_services_default,
     rclcpp::CallbackGroup::SharedPtr group = nullptr);
 
-  /* Create and return a Service. */
+  /// Create and return a Service.
+  /**
+   * \param[in] service_name The topic to service on.
+   * \param[in] callback User-defined callback function.
+   * \param[in] rmw_qos_profile_t Quality of service profile for client.
+   * \param[in] group Callback group to call the service.
+   * \return Shared pointer to the created service.
+   */
   template<typename ServiceT, typename CallbackT>
   typename rclcpp::Service<ServiceT>::SharedPtr
   create_service(
diff --git a/rclcpp/include/rclcpp/parameter.hpp b/rclcpp/include/rclcpp/parameter.hpp
index e01d5aa772..68147ed731 100644
--- a/rclcpp/include/rclcpp/parameter.hpp
+++ b/rclcpp/include/rclcpp/parameter.hpp
@@ -83,18 +83,22 @@ class Parameter
   bool
   operator!=(const Parameter & rhs) const;
 
+  /// Get the type of the parameter
   RCLCPP_PUBLIC
   ParameterType
   get_type() const;
 
+  /// Get the type name of the parameter
   RCLCPP_PUBLIC
   std::string
   get_type_name() const;
 
+  /// Get the name of the parameter
   RCLCPP_PUBLIC
   const std::string &
   get_name() const;
 
+  /// Get value of parameter as a parameter message.
   RCLCPP_PUBLIC
   rcl_interfaces::msg::ParameterValue
   get_value_message() const;
@@ -105,6 +109,9 @@ class Parameter
   get_parameter_value() const;
 
   /// Get value of parameter using rclcpp::ParameterType as template argument.
+  /**
+   * \throws rclcpp::exceptions::InvalidParameterTypeException if the type doesn't match
+   */
   template<ParameterType ParamT>
   decltype(auto)
   get_value() const
@@ -117,50 +124,89 @@ class Parameter
   decltype(auto)
   get_value() const;
 
+  /// Get value of parameter as boolean.
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   bool
   as_bool() const;
 
+  /// Get value of parameter as integer.
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   int64_t
   as_int() const;
 
+  /// Get value of parameter as double.
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   double
   as_double() const;
 
+  /// Get value of parameter as string.
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::string &
   as_string() const;
 
+  /// Get value of parameter as byte array (vector<uint8_t>).
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::vector<uint8_t> &
   as_byte_array() const;
 
+  /// Get value of parameter as bool array (vector<bool>).
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::vector<bool> &
   as_bool_array() const;
 
+  /// Get value of parameter as integer array (vector<int64_t>).
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::vector<int64_t> &
   as_integer_array() const;
 
+  /// Get value of parameter as double array (vector<double>).
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::vector<double> &
   as_double_array() const;
 
+  /// Get value of parameter as string array (vector<std::string>).
+  /**
+   * \throws rclcpp::ParameterTypeException if the type doesn't match
+   */
   RCLCPP_PUBLIC
   const std::vector<std::string> &
   as_string_array() const;
 
+  /// Convert a parameter message in a Parameter class object.
   RCLCPP_PUBLIC
   static Parameter
   from_parameter_msg(const rcl_interfaces::msg::Parameter & parameter);
 
+  /// Convert the class in a parameter message.
   RCLCPP_PUBLIC
   rcl_interfaces::msg::Parameter
   to_parameter_msg() const;
 
+  /// Get value of parameter as a string.
   RCLCPP_PUBLIC
   std::string
   value_to_string() const;
diff --git a/rclcpp/include/rclcpp/publisher.hpp b/rclcpp/include/rclcpp/publisher.hpp
index abe259b31d..ebe349cd99 100644
--- a/rclcpp/include/rclcpp/publisher.hpp
+++ b/rclcpp/include/rclcpp/publisher.hpp
@@ -59,6 +59,17 @@ class Publisher : public PublisherBase
 
   RCLCPP_SMART_PTR_DEFINITIONS(Publisher<MessageT, AllocatorT>)
 
+  /// Default constructor.
+  /**
+   * The constructor for a Publisher is almost never called directly.
+   * Instead, subscriptions should be instantiated through the function
+   * rclcpp::create_publisher().
+   *
+   * \param[in] node_base NodeBaseInterface pointer that is used in part of the setup.
+   * \param[in] topic Name of the topic to publish to.
+   * \param[in] qos QoS profile for Subcription.
+   * \param[in] options options for the subscription.
+   */
   Publisher(
     rclcpp::node_interfaces::NodeBaseInterface * node_base,
     const std::string & topic,
diff --git a/rclcpp/include/rclcpp/qos.hpp b/rclcpp/include/rclcpp/qos.hpp
index 244ac699dc..ac016efec5 100644
--- a/rclcpp/include/rclcpp/qos.hpp
+++ b/rclcpp/include/rclcpp/qos.hpp
@@ -161,6 +161,18 @@ bool operator==(const QoS & left, const QoS & right);
 RCLCPP_PUBLIC
 bool operator!=(const QoS & left, const QoS & right);
 
+/**
+ * Sensor Data QoS class
+ *    - History: Keep last,
+ *    - Depth: 5,
+ *    - Reliability: Best effort,
+ *    - Durability: Volatile,
+ *    - Deadline: Default,
+ *    - Lifespan: Default,
+ *    - Liveliness: System default,
+ *    - Liveliness lease duration: default,
+ *    - avoid ros namespace conventions: false
+ */
 class RCLCPP_PUBLIC SensorDataQoS : public QoS
 {
 public:
@@ -171,6 +183,18 @@ class RCLCPP_PUBLIC SensorDataQoS : public QoS
   ));
 };
 
+/**
+ * Parameters QoS class
+ *    - History: Keep last,
+ *    - Depth: 1000,
+ *    - Reliability: Reliable,
+ *    - Durability: Volatile,
+ *    - Deadline: Default,
+ *    - Lifespan: Default,
+ *    - Liveliness: System default,
+ *    - Liveliness lease duration: default,
+ *    - Avoid ros namespace conventions: false
+ */
 class RCLCPP_PUBLIC ParametersQoS : public QoS
 {
 public:
@@ -181,6 +205,18 @@ class RCLCPP_PUBLIC ParametersQoS : public QoS
   ));
 };
 
+/**
+ * Services QoS class
+ *    - History: Keep last,
+ *    - Depth: 10,
+ *    - Reliability: Reliable,
+ *    - Durability: Volatile,
+ *    - Deadline: Default,
+ *    - Lifespan: Default,
+ *    - Liveliness: System default,
+ *    - Liveliness lease duration: default,
+ *    - Avoid ros namespace conventions: false
+ */
 class RCLCPP_PUBLIC ServicesQoS : public QoS
 {
 public:
@@ -191,6 +227,18 @@ class RCLCPP_PUBLIC ServicesQoS : public QoS
   ));
 };
 
+/**
+ * Parameter events QoS class
+ *    - History: Keep last,
+ *    - Depth: 1000,
+ *    - Reliability: Reliable,
+ *    - Durability: Volatile,
+ *    - Deadline: Default,
+ *    - Lifespan: Default,
+ *    - Liveliness: System default,
+ *    - Liveliness lease duration: default,
+ *    - Avoid ros namespace conventions: false
+ */
 class RCLCPP_PUBLIC ParameterEventsQoS : public QoS
 {
 public:
@@ -201,6 +249,18 @@ class RCLCPP_PUBLIC ParameterEventsQoS : public QoS
   ));
 };
 
+/**
+ * System defaults QoS class
+ *    - History: System default,
+ *    - Depth: System default,
+ *    - Reliability: System default,
+ *    - Durability: System default,
+ *    - Deadline: Default,
+ *    - Lifespan: Default,
+ *    - Liveliness: System default,
+ *    - Liveliness lease duration: System default,
+ *    - Avoid ros namespace conventions: false
+ */
 class RCLCPP_PUBLIC SystemDefaultsQoS : public QoS
 {
 public:
diff --git a/rclcpp/include/rclcpp/rclcpp.hpp b/rclcpp/include/rclcpp/rclcpp.hpp
index 556085ee07..dc22c7e649 100644
--- a/rclcpp/include/rclcpp/rclcpp.hpp
+++ b/rclcpp/include/rclcpp/rclcpp.hpp
@@ -128,6 +128,7 @@
  *   - rclcpp/context.hpp
  *   - rclcpp/contexts/default_context.hpp
  * - Various utilities:
+ *   - rclcpp/duration.hpp
  *   - rclcpp/function_traits.hpp
  *   - rclcpp/macros.hpp
  *   - rclcpp/scope_exit.hpp
diff --git a/rclcpp/include/rclcpp/service.hpp b/rclcpp/include/rclcpp/service.hpp
index de720109a6..abe25867f0 100644
--- a/rclcpp/include/rclcpp/service.hpp
+++ b/rclcpp/include/rclcpp/service.hpp
@@ -50,14 +50,26 @@ class ServiceBase
   RCLCPP_PUBLIC
   virtual ~ServiceBase();
 
+  /// Return the name of the service.
+  /** \return The name of the service. */
   RCLCPP_PUBLIC
   const char *
   get_service_name();
 
+  /// Return the rcl_service_t service handle in a std::shared_ptr.
+  /**
+   * This handle remains valid after the Service is destroyed.
+   * The actual rcl service is not finalized until it is out of scope everywhere.
+   */
   RCLCPP_PUBLIC
   std::shared_ptr<rcl_service_t>
   get_service_handle();
 
+  /// Return the rcl_service_t service handle in a std::shared_ptr.
+  /**
+   * This handle remains valid after the Service is destroyed.
+   * The actual rcl service is not finalized until it is out of scope everywhere.
+   */
   RCLCPP_PUBLIC
   std::shared_ptr<const rcl_service_t>
   get_service_handle() const;
diff --git a/rclcpp/include/rclcpp/subscription.hpp b/rclcpp/include/rclcpp/subscription.hpp
index 2b8108fc94..97e8714b40 100644
--- a/rclcpp/include/rclcpp/subscription.hpp
+++ b/rclcpp/include/rclcpp/subscription.hpp
@@ -90,9 +90,14 @@ class Subscription : public SubscriptionBase
    * \param[in] node_base NodeBaseInterface pointer that is used in part of the setup.
    * \param[in] type_support_handle rosidl type support struct, for the Message type of the topic.
    * \param[in] topic_name Name of the topic to subscribe to.
+   * \param[in] qos QoS profile for Subcription.
    * \param[in] callback User defined callback to call when a message is received.
    * \param[in] options options for the subscription.
    * \param[in] message_memory_strategy The memory strategy to be used for managing message memory.
+   * \param[in] subscription_topic_statistics pointer to a topic statistics subcription.
+   * \throws std::invalid_argument if the QoS is uncompatible with intra-process (if one
+   *   of the following conditions are true: qos_profile.history == RMW_QOS_POLICY_HISTORY_KEEP_ALL,
+   *   qos_profile.depth == 0 or qos_profile.durability != RMW_QOS_POLICY_DURABILITY_VOLATILE).
    */
   Subscription(
     rclcpp::node_interfaces::NodeBaseInterface * node_base,
diff --git a/rclcpp/include/rclcpp/subscription_options.hpp b/rclcpp/include/rclcpp/subscription_options.hpp
index 12275d74fe..5088f35fb1 100644
--- a/rclcpp/include/rclcpp/subscription_options.hpp
+++ b/rclcpp/include/rclcpp/subscription_options.hpp
@@ -89,6 +89,10 @@ struct SubscriptionOptionsWithAllocator : public SubscriptionOptionsBase
   {}
 
   /// Convert this class, with a rclcpp::QoS, into an rcl_subscription_options_t.
+  /**
+   * \param qos QoS profile for subcription.
+   * \return rcl_subscription_options_t structure based on the rclcpp::QoS
+   */
   template<typename MessageT>
   rcl_subscription_options_t
   to_rcl_subscription_options(const rclcpp::QoS & qos) const
diff --git a/rclcpp/include/rclcpp/time.hpp b/rclcpp/include/rclcpp/time.hpp
index d8f65c8672..a80201a356 100644
--- a/rclcpp/include/rclcpp/time.hpp
+++ b/rclcpp/include/rclcpp/time.hpp
@@ -31,26 +31,54 @@ class Clock;
 class Time
 {
 public:
+  /// Time constructor
+  /**
+   * Initializes the time values for seconds and nanoseconds individually.
+   * Large values for nanoseconds are wrapped automatically with the remainder added to seconds.
+   * Both inputs must be integers.
+   *
+   * \param seconds part of the time in seconds since time epoch
+   * \param nanoseconds part of the time in nanoseconds since time epoch
+   * \param clock_type clock type
+   */
   RCLCPP_PUBLIC
   Time(int32_t seconds, uint32_t nanoseconds, rcl_clock_type_t clock_type = RCL_SYSTEM_TIME);
 
+  /// Time constructor
+  /**
+   * \param nanoseconds since time epoch
+   * \param clock_type clock type
+   */
   RCLCPP_PUBLIC
   explicit Time(int64_t nanoseconds = 0, rcl_clock_type_t clock = RCL_SYSTEM_TIME);
 
+  /// Copy constructor
   RCLCPP_PUBLIC
   Time(const Time & rhs);
 
+  /// Time constructor
+  /**
+   * \param time_msg builtin_interfaces time message to copy
+   * \param clock_type clock type
+   */
   RCLCPP_PUBLIC
   Time(
     const builtin_interfaces::msg::Time & time_msg,
     rcl_clock_type_t ros_time = RCL_ROS_TIME);
 
+  /// Time constructor
+  /**
+   * \param time_point rcl_time_point_t structure to copy
+   * \param clock_type clock type
+   */
   RCLCPP_PUBLIC
   explicit Time(const rcl_time_point_t & time_point);
 
+  /// Time destructor
   RCLCPP_PUBLIC
   virtual ~Time();
 
+  /// Return a builtin_interfaces::msg::Time object based
   RCLCPP_PUBLIC
   operator builtin_interfaces::msg::Time() const;
 
@@ -106,21 +134,37 @@ class Time
   Time &
   operator-=(const rclcpp::Duration & rhs);
 
+  /// Get the nanoseconds since epoch
+  /**
+   * \return the nanoseconds since epoch as a rcl_time_point_value_t structure.
+   */
   RCLCPP_PUBLIC
   rcl_time_point_value_t
   nanoseconds() const;
 
+  /// Get the maximum representable value.
+  /**
+   * \return the maximum representable value
+   */
   RCLCPP_PUBLIC
   static Time
   max();
 
-  /// \return the seconds since epoch as a floating point number.
-  /// \warning Depending on sizeof(double) there could be significant precision loss.
-  /// When an exact time is required use nanoseconds() instead.
+  /// Get the seconds since epoch
+  /**
+   * \warning Depending on sizeof(double) there could be significant precision loss.
+   * When an exact time is required use nanoseconds() instead.
+   *
+   * \return the seconds since epoch as a floating point number.
+   */
   RCLCPP_PUBLIC
   double
   seconds() const;
 
+  /// Get the clock type
+  /**
+   * \return the clock type
+   */
   RCLCPP_PUBLIC
   rcl_clock_type_t
   get_clock_type() const;
diff --git a/rclcpp/include/rclcpp/time_source.hpp b/rclcpp/include/rclcpp/time_source.hpp
index 9dd4023d42..86f62a6cab 100644
--- a/rclcpp/include/rclcpp/time_source.hpp
+++ b/rclcpp/include/rclcpp/time_source.hpp
@@ -35,15 +35,42 @@ class Clock;
 class TimeSource
 {
 public:
+  /// Constructor
+  /**
+   * The node will be attached to the time source.
+   *
+   * \param node std::shared pointer to a initialized node
+   */
   RCLCPP_PUBLIC
   explicit TimeSource(rclcpp::Node::SharedPtr node);
 
+  /// Empty constructor
+  /**
+   * An Empty TimeSource class
+   */
   RCLCPP_PUBLIC
   TimeSource();
 
+  /// Attack node to the time source.
+  /**
+   * \param node std::shared pointer to a initialized node
+   */
   RCLCPP_PUBLIC
   void attachNode(rclcpp::Node::SharedPtr node);
 
+  /// Attack node to the time source.
+  /**
+   * If the parameter `use_sim_time` is `true` then the source time is the simulation time,
+   * otherwise the source time is defined by the system.
+   *
+   * \param node_base_interface Node base interface.
+   * \param node_topics_interface Node topic base interface.
+   * \param node_graph_interface Node graph interface.
+   * \param node_services_interface Node service interface.
+   * \param node_logging_interface Node logging interface.
+   * \param node_clock_interface Node clock interface.
+   * \param node_parameters_interface Node parameters interface.
+   */
   RCLCPP_PUBLIC
   void attachNode(
     rclcpp::node_interfaces::NodeBaseInterface::SharedPtr node_base_interface,
@@ -54,19 +81,22 @@ class TimeSource
     rclcpp::node_interfaces::NodeClockInterface::SharedPtr node_clock_interface,
     rclcpp::node_interfaces::NodeParametersInterface::SharedPtr node_parameters_interface);
 
+  /// Detach the node from the time source
   RCLCPP_PUBLIC
   void detachNode();
 
   /// Attach a clock to the time source to be updated
   /**
-   * \throws std::invalid_argument if node is nullptr
+   * \throws std::invalid_argument the time source must be a RCL_ROS_TIME otherwise throws an exception
    */
   RCLCPP_PUBLIC
   void attachClock(rclcpp::Clock::SharedPtr clock);
 
+  /// Detach a clock to the time source
   RCLCPP_PUBLIC
   void detachClock(rclcpp::Clock::SharedPtr clock);
 
+  /// TimeSource Destructor
   RCLCPP_PUBLIC
   ~TimeSource();
 
diff --git a/rclcpp/include/rclcpp/timer.hpp b/rclcpp/include/rclcpp/timer.hpp
index dd754c0748..3f3b4d80b7 100644
--- a/rclcpp/include/rclcpp/timer.hpp
+++ b/rclcpp/include/rclcpp/timer.hpp
@@ -48,15 +48,26 @@ class TimerBase
 public:
   RCLCPP_SMART_PTR_DEFINITIONS_NOT_COPYABLE(TimerBase)
 
+  /// TimerBase constructor
+  /**
+   * \param clock A clock to use for time and sleeping
+   * \param period The interval at which the timer fires
+   * \param context node context
+   */
   RCLCPP_PUBLIC
   explicit TimerBase(
     Clock::SharedPtr clock,
     std::chrono::nanoseconds period,
     rclcpp::Context::SharedPtr context);
 
+  /// TimerBase destructor
   RCLCPP_PUBLIC
   ~TimerBase();
 
+  /// Cancel the timer.
+  /**
+   * \throws std::runtime_error if the rcl_timer_cancel returns a failure
+   */
   RCLCPP_PUBLIC
   void
   cancel();
@@ -71,10 +82,15 @@ class TimerBase
   bool
   is_canceled();
 
+  /// Reset the timer.
+  /**
+   * \throws std::runtime_error if the rcl_timer_reset returns a failure
+   */
   RCLCPP_PUBLIC
   void
   reset();
 
+  /// Call the callback function when the timer signal is emitted.
   RCLCPP_PUBLIC
   virtual void
   execute_callback() = 0;
@@ -209,6 +225,8 @@ class GenericTimer : public TimerBase
     callback_(*this);
   }
 
+  /// Is the clock steady (i.e. is the time between ticks constant?)
+  /** \return True if the clock used by this timer is steady. */
   bool
   is_steady() override
   {
@@ -233,6 +251,12 @@ class WallTimer : public GenericTimer<FunctorT>
 public:
   RCLCPP_SMART_PTR_DEFINITIONS(WallTimer)
 
+  /// Wall timer constructor
+  /**
+   * \param period The interval at which the timer fires
+   * \param callback The callback function to execute every interval
+   * \param context node context
+   */
   WallTimer(
     std::chrono::nanoseconds period,
     FunctorT && callback,