diff --git a/json-schema/schema.json b/json-schema/schema.json
index df9e8e7..697ea9b 100644
--- a/json-schema/schema.json
+++ b/json-schema/schema.json
@@ -847,7 +847,9 @@
             "properties": {
               "mlm:input": {
                 "type": "array",
+                "minItems": 1,
                 "items": {
+                  "type": "object",
                   "required": [
                     "bands"
                   ],