diff --git a/toybox/vats/counter.js b/toybox/vats/counter.js
index a37f686..ed6c6ca 100644
--- a/toybox/vats/counter.js
+++ b/toybox/vats/counter.js
@@ -1,4 +1,9 @@
-/** A counter whose count lives in the vat's storage. */
+/**
+ * A counter whose count lives in the vat's storage.
+ *
+ * TODO: a durable Exo once vatPowers offers a zone, e.g.
+ * `zone.exoClass("Counter", undefined, () => ({ count: 0 }), { incr() { this.state.count += 1; return this.state.count; } })`
+ */
 export const buildRootObject = ({ Far, storage }) =>
 	Far("counterRoot", {
 		increment: () => {