diff --git a/packages/fast-usdc/package.json b/packages/fast-usdc/package.json
index 88039bda5c1..0643f9bf809 100644
--- a/packages/fast-usdc/package.json
+++ b/packages/fast-usdc/package.json
@@ -50,6 +50,7 @@
     "@endo/far": "^1.1.9",
     "@endo/init": "^1.1.7",
     "@endo/marshal": "^1.6.2",
+    "@endo/nat": "^5.0.13",
     "@endo/pass-style": "^1.4.7",
     "@endo/patterns": "^1.4.7",
     "@endo/promise-kit": "^1.1.8",
diff --git a/packages/fast-usdc/src/cli/operator-commands.js b/packages/fast-usdc/src/cli/operator-commands.js
index daa50724807..06a3fdc01df 100644
--- a/packages/fast-usdc/src/cli/operator-commands.js
+++ b/packages/fast-usdc/src/cli/operator-commands.js
@@ -13,11 +13,13 @@ import { INVITATION_MAKERS_DESC } from '../exos/transaction-feed.js';
 import { CctpTxEvidenceShape } from '../type-guards.js';
 import { outputActionAndHint } from './bridge-action.js';
 
+/** @param {string} arg */
 const parseNat = arg => {
   const n = Nat(BigInt(arg));
   return n;
 };
 
+/** @param {string} arg */
 const parseHex = arg => {
   if (!arg.startsWith('0x')) throw new InvalidArgumentError('not a hex string');
   return arg;