diff --git a/packages/utils/src/typechecks.ts b/packages/utils/src/typechecks.ts
index 664fcc53..40faa05d 100644
--- a/packages/utils/src/typechecks.ts
+++ b/packages/utils/src/typechecks.ts
@@ -1,5 +1,10 @@
 /**
- * Checks if data is a non-null object (i.e. matches the TypeScript object type)
+ * Checks if data is a non-null object (i.e. matches the TypeScript object type).
+ *
+ * Note: this returns true for arrays, which are objects in JavaScript
+ * even though array and object are different types in JSON.
+ *
+ * @see https://www.typescriptlang.org/docs/handbook/basic-types.html#object
  */
 export function isNonNullObject(data: unknown): data is object {
   return typeof data === "object" && data !== null;
diff --git a/packages/utils/types/typechecks.d.ts b/packages/utils/types/typechecks.d.ts
index 3e911797..68c29628 100644
--- a/packages/utils/types/typechecks.d.ts
+++ b/packages/utils/types/typechecks.d.ts
@@ -1,5 +1,10 @@
 /**
- * Checks if data is a non-null object (i.e. matches the TypeScript object type)
+ * Checks if data is a non-null object (i.e. matches the TypeScript object type).
+ *
+ * Note: this returns true for arrays, which are objects in JavaScript
+ * even though array and object are different types in JSON.
+ *
+ * @see https://www.typescriptlang.org/docs/handbook/basic-types.html#object
  */
 export declare function isNonNullObject(data: unknown): data is object;
 /**