diff --git a/SAS/TMSS/src/tmss/tmssapp/schemas/scheduling_constraints_template-constraints-1.json b/SAS/TMSS/src/tmss/tmssapp/schemas/scheduling_constraints_template-constraints-1.json
index ca8a3f6754ecdb8aee96c52f31ea14a20b4229aa..9caf086d923d583720925e44d47dfbc255f95885 100644
--- a/SAS/TMSS/src/tmss/tmssapp/schemas/scheduling_constraints_template-constraints-1.json
+++ b/SAS/TMSS/src/tmss/tmssapp/schemas/scheduling_constraints_template-constraints-1.json
@@ -17,10 +17,11 @@
     }
   },
   "type": "object",
+  "default": {},
   "properties": {
     "scheduler": {
       "name": "Scheduler",
-      "description": "Which scheduling system will schedule this",
+      "description": "Schedule manually at the 'time.at' moment, of dynamically taking all time constraints into consideration.",
       "type": "string",
       "enum": [
         "manual",
@@ -33,7 +34,7 @@
       "default": {},
       "properties": {
         "at": {
-          "description": "Start at this moment",
+          "description": "Start at this moment. Requires 'scheduler' to be set to 'manual'.",
           "$ref": "http://tmss.lofar.org/api/schemas/commonschematemplate/datetime/1/#/definitions/timestamp"
         },
         "after": {
@@ -106,6 +107,7 @@
         "transit_offset": {
           "description": "Offset window to LST centering",
           "type": "object",
+          "default": {},
           "properties": {
             "from": {
               "type": "number",
@@ -122,6 +124,7 @@
         },
         "min_distance": {
           "type": "object",
+          "default": {},
           "properties": {
             "sun": {
               "$ref": "#/definitions/distance_on_sky",