diff --git a/controller/predicates/has_request_parameter.js b/controller/predicates/has_request_parameter.js
index 921dfc00..4567f4df 100644
--- a/controller/predicates/has_request_parameter.js
+++ b/controller/predicates/has_request_parameter.js
@@ -1,3 +1,4 @@
 const _ = require('lodash');
 
+// returns true IFF req.clean has a key with the supplied name
 module.exports = (parameter) => (req, res) => (_.has(req, ['clean', parameter]));