diff --git a/include/CLI/App.hpp b/include/CLI/App.hpp
index e5a89f34..80c31ba1 100644
--- a/include/CLI/App.hpp
+++ b/include/CLI/App.hpp
@@ -1632,6 +1632,7 @@ class App {
 
 namespace FailureMessage {
 
+/// Printout a clean, simple message on error (the default in CLI11 1.5+)
 inline std::string simple(const App *app, const Error &e) {
     std::string header = std::string(e.what()) + "\n";
     if(app->get_help_ptr() != nullptr)
@@ -1639,6 +1640,7 @@ inline std::string simple(const App *app, const Error &e) {
     return header;
 }
 
+/// Printout the full help string on error (if this fn is set, the old default for CLI11)
 inline std::string help(const App *app, const Error &e) {
     std::string header = std::string("ERROR: ") + e.get_name() + ": " + e.what() + "\n";
     header += app->help();
diff --git a/include/CLI/FormatterFwd.hpp b/include/CLI/FormatterFwd.hpp
index 92bfe651..cfd5fd10 100644
--- a/include/CLI/FormatterFwd.hpp
+++ b/include/CLI/FormatterFwd.hpp
@@ -97,6 +97,8 @@ class FormatterLambda final : public FormatterBase {
     }
 };
 
+/// This is the default Formatter for CLI11. It pretty prints help output, and is broken into quite a few
+/// overridable methods, to be highly customizable with minimal effort.
 class Formatter : public FormatterBase {
   public:
     Formatter() = default;
diff --git a/include/CLI/Option.hpp b/include/CLI/Option.hpp
index 58c2911e..48b0f7b5 100644
--- a/include/CLI/Option.hpp
+++ b/include/CLI/Option.hpp
@@ -30,6 +30,8 @@ using Option_p = std::unique_ptr<Option>;
 
 enum class MultiOptionPolicy { Throw, TakeLast, TakeFirst, Join };
 
+/// This is the CRTP base class for Option and OptionDefaults. It was designed this way
+/// to share parts of the class; an OptionDefaults can copy to an Option.
 template <typename CRTP> class OptionBase {
     friend App;
 
@@ -123,6 +125,8 @@ template <typename CRTP> class OptionBase {
     }
 };
 
+/// This is a version of OptionBase that only supports setting values,
+/// for defaults. It is stored as the default option in an App.
 class OptionDefaults : public OptionBase<OptionDefaults> {
   public:
     OptionDefaults() = default;
@@ -287,7 +291,7 @@ class Option : public OptionBase<Option> {
         return this;
     }
 
-    /// Adds a validator
+    /// Adds a validator. Takes a const string& and returns an error message (empty if conversion/check is okay).
     Option *check(std::function<std::string(const std::string &)> validator) {
         validators_.emplace_back(validator);
         return this;
diff --git a/include/CLI/Timer.hpp b/include/CLI/Timer.hpp
index eb6054cc..5b5732f0 100644
--- a/include/CLI/Timer.hpp
+++ b/include/CLI/Timer.hpp
@@ -17,6 +17,7 @@
 
 namespace CLI {
 
+/// This is a simple timer with pretty printing. Creating the timer starts counting.
 class Timer {
   protected:
     /// This is a typedef to make clocks easier to use
diff --git a/include/CLI/TypeTools.hpp b/include/CLI/TypeTools.hpp
index 9af8ccaa..d7c3d306 100644
--- a/include/CLI/TypeTools.hpp
+++ b/include/CLI/TypeTools.hpp
@@ -12,18 +12,24 @@ namespace CLI {
 
 // Type tools
 
-// We could check to see if C++14 is being used, but it does not hurt to redefine this
-// (even Google does this: https://github.com/google/skia/blob/master/include/private/SkTLogic.h)
-// It is not in the std namespace anyway, so no harm done.
+/// A copy of enable_if_t from C++14, compatible with C++11.
+///
+/// We could check to see if C++14 is being used, but it does not hurt to redefine this
+/// (even Google does this: https://github.com/google/skia/blob/master/include/private/SkTLogic.h)
+/// It is not in the std namespace anyway, so no harm done.
 
 template <bool B, class T = void> using enable_if_t = typename std::enable_if<B, T>::type;
 
+/// Check to see if something is a vector (fail check by default)
 template <typename T> struct is_vector { static const bool value = false; };
 
+/// Check to see if something is a vector (true if actually a vector)
 template <class T, class A> struct is_vector<std::vector<T, A>> { static bool const value = true; };
 
+/// Check to see if something is bool (fail check by default)
 template <typename T> struct is_bool { static const bool value = false; };
 
+/// Check to see if something is bool (true if actually a bool)
 template <> struct is_bool<bool> { static bool const value = true; };
 
 namespace detail {