diff --git a/packages/seroval/src/core/opaque-reference.ts b/packages/seroval/src/core/opaque-reference.ts
index aa21935..38a7e9d 100644
--- a/packages/seroval/src/core/opaque-reference.ts
+++ b/packages/seroval/src/core/opaque-reference.ts
@@ -1,3 +1,6 @@
+/**
+ * An opaque reference allows hiding values from the serializer.
+ */
 export class OpaqueReference<V, R = undefined> {
   constructor(
     public readonly value: V,