Update and begin work on a new data model

module/models/CommonItemData.mjs

@@ -2,13 +2,15 @@ export class CommonItemData extends foundry.abstract.DataModel {
 	static defineSchema() {
 		const fields = foundry.data.fields;
 		return {
-			name: fields.HTMLField({
+			name: fields.StringField({
+				initial: ``,
 				blank: true,
 				trim: true,
 			}),
 			cost: fields.NumberField({
+				initial: null,
 				nullable: true,
-			})
+			}),
 		};
 	};
 };

module/models/DescribedItemData.mjs

@@ -0,0 +1,12 @@
+export class DescribedItemData extends CommonItemData {
+	static defineSchema() {
+		const fields = foundry.data.fields;
+		return mergeObject(super.defineSchema(), {
+			description: fields.StringField({
+				initial: ``,
+				blank: true,
+				trim: true,
+			}),
+		});
+	};
+};