diff --git a/src/google/adk/tools/openapi_tool/auth/credential_exchangers/service_account_exchanger.py b/src/google/adk/tools/openapi_tool/auth/credential_exchangers/service_account_exchanger.py
index 53587f4e6..9833f5c9c 100644
--- a/src/google/adk/tools/openapi_tool/auth/credential_exchangers/service_account_exchanger.py
+++ b/src/google/adk/tools/openapi_tool/auth/credential_exchangers/service_account_exchanger.py
@@ -72,7 +72,9 @@ def exchange_credential(
 
     try:
       if auth_credential.service_account.use_default_credential:
-        credentials, _ = google.auth.default()
+        credentials, _ = google.auth.default(
+            scopes=["https://www.googleapis.com/auth/cloud-platform"],
+        )
       else:
         config = auth_credential.service_account
         credentials = service_account.Credentials.from_service_account_info(