diff --git a/src/reader/spirv/parser_impl.h b/src/reader/spirv/parser_impl.h
index 579d681..c832a05 100644
--- a/src/reader/spirv/parser_impl.h
+++ b/src/reader/spirv/parser_impl.h
@@ -474,7 +474,11 @@
   /// @returns the instruction, or nullptr on error
   const spvtools::opt::Instruction* GetInstructionForTest(uint32_t id) const;
 
+  /// A map of SPIR-V identifiers to builtins
   using BuiltInsMap = std::unordered_map<uint32_t, SpvBuiltIn>;
+
+  /// @returns a map of builtins that should be ignored as they do not exist in
+  /// WGSL.
   const BuiltInsMap& ignored_builtins() const { return ignored_builtins_; }
 
  private: