diff --git a/src/stages/ast_simplified/types.ml b/src/stages/ast_simplified/types.ml
index 69f564740..a941bf8fb 100644
--- a/src/stages/ast_simplified/types.ml
+++ b/src/stages/ast_simplified/types.ml
@@ -11,7 +11,14 @@ and type_expression =  {
   }
 and declaration =
   | Declaration_type of (type_variable * type_expression)
+
+  (* A Declaration_constant is described by
+   *   a name
+   *   an optional type annotation
+   *   a boolean indicating whether it should be inlined
+   *   an expression *)
   | Declaration_constant of (expression_variable * type_expression option * inline * expression)
+
   (* | Macro_declaration of macro_declaration *)
 
 and expr = expression
diff --git a/src/stages/ast_typed/types.ml b/src/stages/ast_typed/types.ml
index cf4957613..d153a1cff 100644
--- a/src/stages/ast_typed/types.ml
+++ b/src/stages/ast_typed/types.ml
@@ -8,7 +8,13 @@ type program = declaration Location.wrap list
 and inline = bool
 
 and declaration =
+  (* A Declaration_constant is described by
+   *   a name + a type-annotated expression
+   *   a boolean indicating whether it should be inlined
+   *   the environment before the declaration (the original environment)
+   *   the environment after the declaration (i.e. with that new declaration added to the original environment). *)
   | Declaration_constant of (named_expression * inline * (full_environment * full_environment))
+
   (* | Macro_declaration of macro_declaration *)
 
 and environment_element_definition =