diff --git a/rosidl_typesupport_introspection_c/bin/rosidl_typesupport_introspection_c b/rosidl_typesupport_introspection_c/bin/rosidl_typesupport_introspection_c
index c9504656a..e20111d5b 100755
--- a/rosidl_typesupport_introspection_c/bin/rosidl_typesupport_introspection_c
+++ b/rosidl_typesupport_introspection_c/bin/rosidl_typesupport_introspection_c
@@ -4,9 +4,17 @@ import argparse
 import sys
 
 from rosidl_typesupport_introspection_c import generate_c
+from typing import List
 
 
-def main(argv=sys.argv[1:]):
+def main(argv: List[str] = sys.argv[1:]):
+    """
+    Generate the C introspection type support for ROS interfaces.
+
+    :param argv: The command-line arguments to be parsed. Defaults to
+        sys.argv[1:].
+    :type argv: List[str]
+    """
     parser = argparse.ArgumentParser(
         description='Generate the C type support to dynamically handle ROS messages.',
         formatter_class=argparse.ArgumentDefaultsHelpFormatter)
diff --git a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/field_types.h b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/field_types.h
index 30547b82b..cd336cd3b 100644
--- a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/field_types.h
+++ b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/field_types.h
@@ -22,32 +22,56 @@ extern "C"
 {
 #endif
 
-enum
+/// Possible types for message fields on a ROS message
+/// The equivalent OMG IDL and C types of the different fields can be found
+/// at http://design.ros2.org/articles/idl_interface_definition.html#type-mapping
+enum rosidl_typesupport_introspection_c_field_types
 {
+  /// Equivalent to float in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT = 1,
+  /// Equivalent to double in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_DOUBLE = 2,
+  /// Equivalent to long double in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_LONG_DOUBLE = 3,
+  /// Equivalent to unsigned char in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_CHAR = 4,
+  /// Equivalent to char16_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_WCHAR = 5,
+  /// Equivalent to _Bool in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_BOOLEAN = 6,
+  /// Equivalent to unsigned char in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_OCTET = 7,
+  /// Equivalent to uint8_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_UINT8 = 8,
+  /// Equivalent to int8_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_INT8 = 9,
+  /// Equivalent to uint16_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_UINT16 = 10,
+  /// Equivalent to int16_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_INT16 = 11,
+  /// Equivalent to uint32_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_UINT32 = 12,
+  /// Equivalent to int32_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_INT32 = 13,
+  /// Equivalent to uint64_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_UINT64 = 14,
+  /// Equivalent to int64_t in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_INT64 = 15,
+  /// Equivalent to char * in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_STRING = 16,
+  /// Equivalent to char16_t * in C types.
   rosidl_typesupport_introspection_c__ROS_TYPE_WSTRING = 17,
 
+  /// An embedded message type.
   rosidl_typesupport_introspection_c__ROS_TYPE_MESSAGE = 18,
 
-  // for backward compatibility only
+  /// For backward compatibility only.
   rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT32 = 1,
+  /// For backward compatibility only.
   rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT64 = 2,
+  /// For backward compatibility only.
   rosidl_typesupport_introspection_c__ROS_TYPE_BOOL = 6,
+  /// For backward compatibility only.
   rosidl_typesupport_introspection_c__ROS_TYPE_BYTE = 7
 };
 
diff --git a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/identifier.h b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/identifier.h
index 889831c0f..32f545536 100644
--- a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/identifier.h
+++ b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/identifier.h
@@ -22,6 +22,7 @@ extern "C"
 {
 #endif
 
+/// String identifying the typesupport introspection implementation in use.
 ROSIDL_TYPESUPPORT_INTROSPECTION_C_PUBLIC
 extern const char * rosidl_typesupport_introspection_c__identifier;
 
diff --git a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/message_introspection.h b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/message_introspection.h
index f504e0c83..d5d220e08 100644
--- a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/message_introspection.h
+++ b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/message_introspection.h
@@ -24,19 +24,39 @@
 
 #include "rosidl_typesupport_introspection_c/visibility_control.h"
 
+/// Structure used to describe a single field of an interface type.
 typedef struct rosidl_typesupport_introspection_c__MessageMember_s
 {
+  /// The name of the field.
   const char * name_;
+  /// The type of the field as a value of the field types enum
+  /// rosidl_typesupport_introspection_c_field_types.
+  /// e.g. rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT
   uint8_t type_id_;
+  /// If the field is a string, the upper bound on the length of the string.
   size_t string_upper_bound_;
+  /// If the type_id_ value is rosidl_typesupport_introspection_c__ROS_TYPE_MESSAGE,
+  /// this points to an array describing the fields of the sub-interface.
   const rosidl_message_type_support_t * members_;
+  /// True if this field is an array type, false if it is any other type. An
+  /// array has the same value for / type_id_.
   bool is_array_;
+  /// If is_array_ is true, this contains the number of members in the array.
   size_t array_size_;
+  /// If is_array_ is true, this specifies if the array has a maximum size. If it is true, the
+  /// value in array_size_ is the maximum size.
   bool is_upper_bound_;
+  /// The bytes into the interface's in-memory representation that this field can be found at.
   uint32_t offset_;
+  /// If the interface has a default value, this points to it.
   const void * default_value_;
+  /// If is_array_ is true, a pointer to a function that gives the size of one member of the array.
   size_t (* size_function)(const void *);
+  /// If is_array_ is true, a pointer to a function that gives a const pointer to the member of the
+  /// array indicated by index.
   const void * (*get_const_function)(const void *, size_t index);
+  /// If is_array_ is true, a pointer to a function that gives a pointer to the member of the
+  /// array indicated by index.
   void * (*get_function)(void *, size_t index);
   /// Pointer to a function that fetches (i.e. copies) an item from
   /// an array or sequence member. It takes a pointer to the member,
@@ -53,17 +73,27 @@ typedef struct rosidl_typesupport_introspection_c__MessageMember_s
   ///
   /// Available for array and sequence members.
   void (* assign_function)(void *, size_t index, const void *);
+  /// If is_array_ is true, a pointer to a function that resizes the array.
   bool (* resize_function)(void *, size_t size);
 } rosidl_typesupport_introspection_c__MessageMember;
 
+/// Structure used to describe all fields of a single interface type.
 typedef struct rosidl_typesupport_introspection_c__MessageMembers_s
 {
+  /// The namespace in which the interface resides, e.g. "example_messages__msg" for
+  /// example_messages/msg
   const char * message_namespace_;
+  /// The name of the interface, e.g. "Int16"
   const char * message_name_;
+  /// The number of fields in the interface
   uint32_t member_count_;
+  /// The size of the interface structure in memory
   size_t size_of_;
+  /// A pointer to the array that describes each field of the interface
   const rosidl_typesupport_introspection_c__MessageMember * members_;
+  /// The function used to initialise the interface's in-memory representation
   void (* init_function)(void *, enum rosidl_runtime_c__message_initialization);
+  /// The function used to clean up the interface's in-memory representation
   void (* fini_function)(void *);
 } rosidl_typesupport_introspection_c__MessageMembers;
 
diff --git a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/service_introspection.h b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/service_introspection.h
index 60709bb55..059ab00fc 100644
--- a/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/service_introspection.h
+++ b/rosidl_typesupport_introspection_c/include/rosidl_typesupport_introspection_c/service_introspection.h
@@ -23,11 +23,18 @@
 
 #include "rosidl_typesupport_introspection_c/message_introspection.h"
 
+/// This struct provides introspection information for one service definition.
+/// A service is comprised of two interfaces: the request and the response.
 typedef struct rosidl_typesupport_introspection_c__ServiceMembers_s
 {
+  /// The namespace in which the service resides, e.g. "example_messages__srv" for
+  /// example_messages/srv
   const char * service_namespace_;
+  /// The name of the service, e.g. "AddTwoInts"
   const char * service_name_;
+  /// A pointer to the introspection information structure for the request interface.
   const rosidl_typesupport_introspection_c__MessageMembers * request_members_;
+  /// A pointer to the introspection information structure for the response interface.
   const rosidl_typesupport_introspection_c__MessageMembers * response_members_;
 } rosidl_typesupport_introspection_c__ServiceMembers;
 
diff --git a/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/__init__.py b/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/__init__.py
index e47caee3b..fba92d457 100644
--- a/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/__init__.py
+++ b/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/__init__.py
@@ -1,4 +1,4 @@
-# Copyright 2014-2018 Open Source Robotics Foundation, Inc.
+# Copyright 2014-2021 Open Source Robotics Foundation, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,7 +15,14 @@
 from rosidl_cmake import generate_files
 
 
-def generate_c(generator_arguments_file):
+def generate_c(generator_arguments_file: str):
+    """
+    Generate the C implementation of the type support.
+
+    :param generator_arguments_file: The path to the file containing the
+        arguments for the generator.
+    :type generator_arguments_file: str
+    """
     mapping = {
         'idl__rosidl_typesupport_introspection_c.h.em':
         'detail/%s__rosidl_typesupport_introspection_c.h',
diff --git a/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/cli.py b/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/cli.py
index 4b5ebc54b..3cee143ce 100644
--- a/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/cli.py
+++ b/rosidl_typesupport_introspection_c/rosidl_typesupport_introspection_c/cli.py
@@ -25,6 +25,7 @@
 
 
 class GenerateIntrospectionCTypesupport(GenerateCommandExtension):
+    """Generate the C type support implementation."""
 
     def generate(
         self,
diff --git a/rosidl_typesupport_introspection_cpp/bin/rosidl_typesupport_introspection_cpp b/rosidl_typesupport_introspection_cpp/bin/rosidl_typesupport_introspection_cpp
index 06c41322a..3e2e2cede 100755
--- a/rosidl_typesupport_introspection_cpp/bin/rosidl_typesupport_introspection_cpp
+++ b/rosidl_typesupport_introspection_cpp/bin/rosidl_typesupport_introspection_cpp
@@ -4,9 +4,17 @@ import argparse
 import sys
 
 from rosidl_typesupport_introspection_cpp import generate_cpp
+from typing import List
 
 
-def main(argv=sys.argv[1:]):
+def main(argv: List[str] = sys.argv[1:]):
+    """
+    Generate the C++ introspection type support for ROS interfaces.
+
+    :param argv: The command-line arguments to be parsed. Defaults to
+        sys.argv[1:].
+    :type argv: List[str]
+    """
     parser = argparse.ArgumentParser(
         description='Generate the C++ type support to dynamically handle ROS messages.',
         formatter_class=argparse.ArgumentDefaultsHelpFormatter)
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/field_types.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/field_types.hpp
index 978cf87f5..dc21f61f2 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/field_types.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/field_types.hpp
@@ -20,31 +20,55 @@
 
 namespace rosidl_typesupport_introspection_cpp
 {
+/// Possible types for message fields on a ROS message
+/// The equivalent OMG IDL and C++ types of the different fields can be found
+/// at http://design.ros2.org/articles/idl_interface_definition.html#type-mapping
 
+/// Equivalent to float in C++ types.
 const uint8_t ROS_TYPE_FLOAT = rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT;
+/// Equivalent to double in C++ types.
 const uint8_t ROS_TYPE_DOUBLE = rosidl_typesupport_introspection_c__ROS_TYPE_DOUBLE;
+/// Equivalent to long double in C++ types.
 const uint8_t ROS_TYPE_LONG_DOUBLE = rosidl_typesupport_introspection_c__ROS_TYPE_LONG_DOUBLE;
+/// Equivalent to unsigned char in C++ types.
 const uint8_t ROS_TYPE_CHAR = rosidl_typesupport_introspection_c__ROS_TYPE_CHAR;
+/// Equivalent to char16_t in C++ types.
 const uint8_t ROS_TYPE_WCHAR = rosidl_typesupport_introspection_c__ROS_TYPE_WCHAR;
+/// Equivalent to bool in C++ types.
 const uint8_t ROS_TYPE_BOOLEAN = rosidl_typesupport_introspection_c__ROS_TYPE_BOOLEAN;
+/// Equivalent to std::byte in C++ types.
 const uint8_t ROS_TYPE_OCTET = rosidl_typesupport_introspection_c__ROS_TYPE_OCTET;
+/// Equivalent to uint8_t in C++ types.
 const uint8_t ROS_TYPE_UINT8 = rosidl_typesupport_introspection_c__ROS_TYPE_UINT8;
+/// Equivalent to int8_t in C++ types.
 const uint8_t ROS_TYPE_INT8 = rosidl_typesupport_introspection_c__ROS_TYPE_INT8;
+/// Equivalent to uint16_t in C++ types.
 const uint8_t ROS_TYPE_UINT16 = rosidl_typesupport_introspection_c__ROS_TYPE_UINT16;
+/// Equivalent to int16_t in C++ types.
 const uint8_t ROS_TYPE_INT16 = rosidl_typesupport_introspection_c__ROS_TYPE_INT16;
+/// Equivalent to uint32_t in C++ types.
 const uint8_t ROS_TYPE_UINT32 = rosidl_typesupport_introspection_c__ROS_TYPE_UINT32;
+/// Equivalent to int32_t in C++ types.
 const uint8_t ROS_TYPE_INT32 = rosidl_typesupport_introspection_c__ROS_TYPE_INT32;
+/// Equivalent to uint64_t in C++ types.
 const uint8_t ROS_TYPE_UINT64 = rosidl_typesupport_introspection_c__ROS_TYPE_UINT64;
+/// Equivalent to int64_t in C++ types.
 const uint8_t ROS_TYPE_INT64 = rosidl_typesupport_introspection_c__ROS_TYPE_INT64;
+/// Equivalent to std::string in C++ types.
 const uint8_t ROS_TYPE_STRING = rosidl_typesupport_introspection_c__ROS_TYPE_STRING;
+/// Equivalent to std::u16string in C++ types.
 const uint8_t ROS_TYPE_WSTRING = rosidl_typesupport_introspection_c__ROS_TYPE_WSTRING;
 
+/// An embedded message type.
 const uint8_t ROS_TYPE_MESSAGE = rosidl_typesupport_introspection_c__ROS_TYPE_MESSAGE;
 
-// for backward compatibility only
+/// For backward compatibility only.
 const uint8_t ROS_TYPE_BOOL = rosidl_typesupport_introspection_c__ROS_TYPE_BOOL;
+/// For backward compatibility only.
 const uint8_t ROS_TYPE_BYTE = rosidl_typesupport_introspection_c__ROS_TYPE_BYTE;
+/// For backward compatibility only.
 const uint8_t ROS_TYPE_FLOAT32 = rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT32;
+/// For backward compatibility only.
 const uint8_t ROS_TYPE_FLOAT64 = rosidl_typesupport_introspection_c__ROS_TYPE_FLOAT64;
 
 }  // namespace rosidl_typesupport_introspection_cpp
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/identifier.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/identifier.hpp
index f72410c69..26d875511 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/identifier.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/identifier.hpp
@@ -20,6 +20,7 @@
 namespace rosidl_typesupport_introspection_cpp
 {
 
+/// String identifying the typesupport introspection implementation in use.
 ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_IMPORT
 extern const char * typesupport_identifier;
 
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_introspection.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_introspection.hpp
index 6a76a6790..2340f2c8c 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_introspection.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_introspection.hpp
@@ -27,19 +27,41 @@
 namespace rosidl_typesupport_introspection_cpp
 {
 
+/// Structure used to describe a single field of an interface type.
 typedef struct ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC MessageMember_s
 {
+  /// The name of the field.
   const char * name_;
+  /// The type of the field as a value of the field types enum,
+  /// e.g.rosidl_typesupport_introspection_cpp::ROS_TYPE_FLOAT
   uint8_t type_id_;
+  /// If the field is a string, the upper bound on the length of the string.
   size_t string_upper_bound_;
+  /// If the type_id_ value is rosidl_typesupport_introspection_cpp::ROS_TYPE_MESSAGE
+  /// this points to an array describing the fields of the sub-interface.
   const rosidl_message_type_support_t * members_;
+  /// True if this field is an array, false if it is a unary type. An array has the same value for
+  /// type_id_.
   bool is_array_;
+  /// If is_array_ is true, this contains the number of members in the array.
   size_t array_size_;
+  /// If is_array_ is true, this specifies if the array has a maximum size. If it is true, the
+  /// value in array_size_ is the maximum size.
   bool is_upper_bound_;
+  /// The bytes into the interface's in-memory representation that this field can be found at.
   uint32_t offset_;
+  /// If the interface has a default value, this points to it.
   const void * default_value_;
+  /// If is_array_ is true, a pointer to a function that gives the size of array members.
+  /// First argument should be a pointer to the actual memory representation of the member.
   size_t (* size_function)(const void *);
+  /// If is_array_ is true, a pointer to a function that gives a const pointer to the member of the
+  /// array indicated by index.
+  /// First argument should be a pointer to the actual memory representation of the member.
   const void * (*get_const_function)(const void *, size_t index);
+  /// If is_array_ is true, a pointer to a function that gives a pointer to the member of the
+  /// array indicated by index.
+  /// First argument should be a pointer to the actual memory representation of the member.
   void * (*get_function)(void *, size_t index);
   /// Pointer to a function that fetches (i.e. copies) an item from
   /// an array or sequence member. It takes a pointer to the member,
@@ -56,17 +78,29 @@ typedef struct ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC MessageMember_s
   ///
   /// Available for array and sequence members.
   void (* assign_function)(void *, size_t index, const void *);
+  /// If is_array_ is true, a pointer to a function that resizes the array.
+  /// First argument should be a pointer to the actual memory representation of the member.
   void (* resize_function)(void *, size_t size);
 } MessageMember;
 
+/// Structure used to describe all fields of a single interface type.
 typedef struct ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC MessageMembers_s
 {
+  /// The namespace in which the interface resides, e.g. for
+  /// example_messages/msg the namespaces generated would be
+  /// example_message::msg".
   const char * message_namespace_;
+  /// The name of the interface, e.g. "Int16"
   const char * message_name_;
+  /// The number of fields in the interface
   uint32_t member_count_;
+  /// The size of the interface structure in memory
   size_t size_of_;
+  /// A pointer to the array that describes each field of the interface
   const MessageMember * members_;
+  /// The function used to initialise the interface's in-memory representation
   void (* init_function)(void *, rosidl_runtime_cpp::MessageInitialization);
+  /// The function used to clean up the interface's in-memory representation
   void (* fini_function)(void *);
 } MessageMembers;
 
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_type_support_decl.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_type_support_decl.hpp
index 6b7579f52..97eece341 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_type_support_decl.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/message_type_support_decl.hpp
@@ -23,7 +23,10 @@
 namespace rosidl_typesupport_introspection_cpp
 {
 
-// This is implemented in the shared library provided by this package.
+/// Returns a pointer to the type support structure provided by the
+/// downstream libraries for introspecting interfaces generated by
+/// the rosidl_generate_interfaces() macro.
+/// This is implemented in the shared library provided by this package.
 template<typename T>
 ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC
 const rosidl_message_type_support_t * get_message_type_support_handle();
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_introspection.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_introspection.hpp
index 49dcd33eb..df6f910d8 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_introspection.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_introspection.hpp
@@ -26,11 +26,18 @@
 namespace rosidl_typesupport_introspection_cpp
 {
 
+/// This struct provides introspection information for one service definition.
+/// A service is comprised of two interfaces: the request and the response.
 typedef struct ServiceMembers_s
 {
+  /// The namespace in which the service resides, e.g. "example_messages::srv"
+  /// for example_messages/srv
   const char * service_namespace_;
+  /// The name of the service, e.g. "AddTwoInts"
   const char * service_name_;
+  /// A pointer to the introspection information structure for the request interface.
   const MessageMembers * request_members_;
+  /// A pointer to the introspection information structure for the response interface.
   const MessageMembers * response_members_;
 } ServiceMembers;
 
diff --git a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_type_support_decl.hpp b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_type_support_decl.hpp
index 47fa80c33..eaa3db906 100644
--- a/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_type_support_decl.hpp
+++ b/rosidl_typesupport_introspection_cpp/include/rosidl_typesupport_introspection_cpp/service_type_support_decl.hpp
@@ -23,7 +23,9 @@
 namespace rosidl_typesupport_introspection_cpp
 {
 
-// This is implemented in the shared library provided by this package.
+/// Returns a pointer to the type support structure provided by this library for introspecting
+/// services.
+/// This is implemented in the shared library provided by this package.
 template<typename T>
 ROSIDL_TYPESUPPORT_INTROSPECTION_CPP_PUBLIC
 const rosidl_service_type_support_t * get_service_type_support_handle();
diff --git a/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/__init__.py b/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/__init__.py
index c4a66072a..b8a901d7e 100644
--- a/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/__init__.py
+++ b/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/__init__.py
@@ -15,7 +15,14 @@
 from rosidl_cmake import generate_files
 
 
-def generate_cpp(generator_arguments_file):
+def generate_cpp(generator_arguments_file: str):
+    """
+    Generate the C++ implementation of the type support.
+
+    :param generator_arguments_file: The path to the file containing the
+        arguments for the generator.
+    :type generator_arguments_file: str
+    """
     mapping = {
         'idl__rosidl_typesupport_introspection_cpp.hpp.em':
         'detail/%s__rosidl_typesupport_introspection_cpp.hpp',
diff --git a/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/cli.py b/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/cli.py
index 80b776de4..a26b5d99d 100644
--- a/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/cli.py
+++ b/rosidl_typesupport_introspection_cpp/rosidl_typesupport_introspection_cpp/cli.py
@@ -24,6 +24,7 @@
 
 
 class GenerateIntrospectionCppTypesupport(GenerateCommandExtension):
+    """Make up a CLI for convenient access to the generators of type support."""
 
     def generate(
         self,