after change of json i get this error "Value should be a JSON object"

[BlackCrystal]

I've got this discovery that i use it for my Disk IO monitoring. the json data for this discovery is like this:

{
"data":[
{ "{#DEVICE_NAME}":"/dev/sde1" },
{ "{#DEVICE_NAME}":"/dev/sdf1" }
]
}

and it works perfectly. then i added another field:

{
"data":[
{ "{#OS_FS}":"/dev/sdb1", "{#DEFINED_FS}":"/data1" },
{ "{#OS_FS}":"/dev/sdd1", "{#DEFINED_FS}":"/data3" },
{ "{#OS_FS}":"/dev/sdc1", "{#DEFINED_FS}":"/data2" }
]
}

and i got this error "Value should be a JSON object" when i added my host to template with this discovery. i used online json validators and these formats are correct.
what should i do?