diff --git a/farm_control.lua b/farm_control.lua
index 5c9b459..e199bb4 100644
--- a/farm_control.lua
+++ b/farm_control.lua
@@ -8,6 +8,7 @@ local STORAGE = ""
 local HARVESTER = ""
 local PLANTER = ""
 
+-- format: `{relay_name}:{side}`
 local HARVESTER_RELAY = ""
 local PLANTER_RELAY = ""