diff --git a/except.cpp b/except.cpp
index 0943c03e..d932d089 100644
--- a/except.cpp
+++ b/except.cpp
@@ -26,12 +26,18 @@
 using namespace std;
 
 
+/// Construct an errno_error from a given error value. The error value MUST signal an error at
+/// construction time.
 errno_error::errno_error (int _errno):
     runtime_error (strerror (_errno)),
     id            (_errno)
-{ ; }
+{
+    check_hard (_errno != 0);
+}
 
 
+/// Construct an errno_error from the current value of errno. errno MUST signal an error at
+/// construction time.
 errno_error::errno_error ():
     runtime_error (strerror (errno)),
     id            (errno)
@@ -40,11 +46,13 @@ errno_error::errno_error ():
 }
 
 
+/// Throw an errno_error exception if errno currently signals an error.
 void
 errno_error::try_code ()
     { try_code (errno); }
 
 
+/// Throw an errno_error exception if 'code' represents an error.
 void
 errno_error::try_code(int code) {
     if (code != 0)
diff --git a/except.hpp b/except.hpp
index 71c5dc68..e8a222f3 100644
--- a/except.hpp
+++ b/except.hpp
@@ -40,6 +40,7 @@ class unavailable_error : public std::runtime_error {
 };
 
 
+/// An exception class used for reporting errors signalled by errno.
 class errno_error : public std::runtime_error {
     public:
         int id;
diff --git a/json.hpp b/json.hpp
index bd265f72..7fcdd64f 100644
--- a/json.hpp
+++ b/json.hpp
@@ -41,6 +41,7 @@ namespace json {
     extern node* parse (const char *start, const char *stop);
     extern node* parse (const char *start);
 
+    /// Abstract base for all JSON values
     class node {
         public:
             virtual ~node () { ; }
@@ -72,6 +73,7 @@ namespace json {
     };                                          
 
 
+    /// Represents a JSON object, and contains its children.
     class object : public node {
         protected:
             std::map<std::string, node*> m_values;
@@ -94,6 +96,7 @@ namespace json {
     };
 
 
+    /// Represents a JSON array, and contains its children.
     class array : public node {
         protected:
             std::vector<node*> m_values;
@@ -126,6 +129,7 @@ namespace json {
     };
 
 
+    /// Represents a JSON string literal.
     class string : public node {
         protected:
             std::string m_value;
@@ -146,6 +150,7 @@ namespace json {
     };
 
 
+    /// Represents a JSON integer/float literal.
     class number : public node {
         protected:
             double m_value;
@@ -166,6 +171,7 @@ namespace json {
     };
 
 
+    /// Represents a JSON boolean literal.
     class boolean : public node {
         protected:
             bool m_value;
@@ -183,6 +189,7 @@ namespace json {
     };
 
 
+    /// Represents a JSON null value.
     class null : public node {
         public:
             virtual bool is_null (void) const { return  true; }
@@ -193,6 +200,7 @@ namespace json {
     };
 
 
+    /// The base class for all exceptions throw directly by the json namespace.
     class error : public std::runtime_error {
         public:
             error (const std::string &_what):
diff --git a/types.hpp b/types.hpp
index e9c5691a..3077fcf5 100644
--- a/types.hpp
+++ b/types.hpp
@@ -98,10 +98,12 @@ size_t elems(T (&)[N])
     { return N; }
 
 
+/// Convert a scalar from host byte order to network byte order
 template <typename T>
 T hton (T);
 
 
+/// Convert a scalar from network byte order to host byte order
 template <typename T>
 T ntoh (T);