diff --git a/src/diagnostic/diagnostic.h b/src/diagnostic/diagnostic.h
index 843a00616e..98175fef06 100644
--- a/src/diagnostic/diagnostic.h
+++ b/src/diagnostic/diagnostic.h
@@ -37,20 +37,31 @@ inline bool operator>=(Severity a, Severity b) {
 /// message.
 class Diagnostic {
  public:
+  /// severity is the severity of the diagnostic message.
   Severity severity = Severity::Error;
+  /// source is the location of the diagnostic.
   Source source;
+  /// message is the text associated with the diagnostic.
   std::string message;
 };
 
 /// List is a container of Diagnostic messages.
 class List {
  public:
+  /// iterator is the type used for range based iteration.
   using iterator = std::vector<Diagnostic>::const_iterator;
 
+  /// Constructs the list with no elements.
   List();
+
+  /// Constructs the list with a copy of the diagnostics in |list|.
+  /// @param list the list of diagnostics to copy into this list.
   List(std::initializer_list<Diagnostic> list);
+
   ~List();
 
+  /// adds a diagnostic to the end of this list.
+  /// @param diag the diagnostic to append to this list.
   void add(Diagnostic&& diag) {
     entries_.emplace_back(std::move(diag));
     if (diag.severity >= Severity::Error) {
diff --git a/src/reader/wgsl/parser_impl.h b/src/reader/wgsl/parser_impl.h
index 8ea3e6cdd3..9a902f4a1d 100644
--- a/src/reader/wgsl/parser_impl.h
+++ b/src/reader/wgsl/parser_impl.h
@@ -81,9 +81,12 @@ class ParserImpl {
   /// TypedIdentifier holds a parsed identifier and type. Returned by
   /// variable_ident_decl().
   struct TypedIdentifier {
-    ast::type::Type* type = nullptr;  /// Parsed type.
-    std::string name;                 /// Parsed identifier.
-    Source source;                    /// Source to the identifier.
+    /// Parsed type.
+    ast::type::Type* type = nullptr;
+    /// Parsed identifier.
+    std::string name;
+    /// Source to the identifier.
+    Source source;
   };
 
   /// Creates a new parser using the given file
diff --git a/src/source.h b/src/source.h
index ffc873ba1b..e26c14a7f5 100644
--- a/src/source.h
+++ b/src/source.h
@@ -44,12 +44,11 @@ class Source {
   };
 
   /// Location holds a 1-based line and column index.
-  /// 0's for |line| or |column| represent invalid values.
   class Location {
    public:
-    /// The line number, 1-based
+    /// the 1-based line number. 0 represents no line information.
     size_t line = 0;
-    /// The column number, 1-based
+    /// the 1-based column number. 0 represents no column information.
     size_t column = 0;
   };
 
@@ -60,12 +59,12 @@ class Source {
     inline Range() = default;
 
     /// Constructs a zero-length Range starting at |loc|.
-    /// @param loc the location to use to build the range
+    /// @param loc the start and end location for the range.
     inline explicit Range(const Location& loc) : begin(loc), end(loc) {}
 
     /// Constructs the Range beginning at |b| and ending at |e|.
-    /// @param b the beginning of the range
-    /// @param e the end of the range
+    /// @param b the range start location.
+    /// @param e the range end location.
     inline Range(const Location& b, const Location& e) : begin(b), end(e) {}
 
     /// The location of the first character in the range.
@@ -78,21 +77,21 @@ class Source {
   inline Source() = default;
 
   /// Constructs the Source with the Range |rng| and a null File.
-  /// @param rng the range to assign to the source
+  /// @param rng the source range
   inline explicit Source(const Range& rng) : range(rng) {}
 
   /// Constructs the Source with the Range |loc| and a null File.
-  /// @param loc the location to assign to the source
+  /// @param loc the start and end location for the source range
   inline explicit Source(const Location& loc) : range(Range(loc)) {}
 
   /// Constructs the Source with the Range |rng| and File |f|.
-  /// @param rng the range for the source
-  /// @param f the file for the source
+  /// @param rng the source range
+  /// @param f the source file
   inline Source(const Range& rng, File const* f) : range(rng), file(f) {}
 
-  /// Line/column range for this source
+  /// range is the span of text this source refers to in |file|
   Range range;
-  /// Source file
+  /// file is the source file this source refers to
   File const* file = nullptr;
 };