how to add an json object as an element to another json - json

Question

i create a json object by a script with jq.
jq -n --arg date "$DATE" --arg script "$SCRIPT" --arg log_level "$LOG_LEVEL" --arg ppid "$PPID" --arg message "$MESSAGE" '{"t":$date, "service":$script, "level":$log_level, "pid":$ppid, "message":$message}'
The Variable log_level and message are provided by another script and in message there can be stored a plain string or a json string.
Example Json String:
{"text":"value", "text2":"value2"}
Output if a a plain string is provided:
{
"t": "2017-10-12 16:52:26",
"service": "import.sh",
"level": "INFO",
"pid": "23425",
"message": "START"
}
Output if a json object is provided:
{
"t": "2017-10-12 17:01:16",
"service": "import.sh",
"level": "INFO",
"pid": "13069",
"message": "{\"text\":\"value\", \"text2\":\"value2\"}"
}
What i expected if i provide the json object:
{
"t": "2017-10-12 17:01:16",
"service": "cis_import.sh",
"level": "INFO",
"pid": "13069",
"message": {
"text": "value",
"text2": "value2"
}
}
Am i right that jq add the \ for each " because it gets added to the json object like it would be a simple string?
How can i get my expected json?

Answer 1

Got it finally. Thanks for the hints chepner
and blusky
To validate if $MESSAGEis a json i use jq -n $MESSAGE see jq manual instead of jq . /path/to/file.json
To use the mentioned --argjson i will add " around $MESSAGEif the $MESSAGE is a plain string MESSAGE="\"$MESSAGE\"". I do this with DATE, SCRIPT, LOG_LEVEL, PPID too.
Command to create the json object looks like this:
jq -cn --argjson date "$DATE" --argjson script "$SCRIPT" --argjson log_level "$LOG_LEVEL" --argjson ppid "$PPID" --argjson message "$MESSAGE" '{"t":$date, "service":$script, "level":$log_level, "pid":$ppid, "message":$message}'