API: create a new Trello card (with labels) via curl

Hello all:
The doc says that I should be able to create a new Trello card with labels. But anytime I try to add idLabels to my POST, I get a 400:

CARDID=$(curl --fail --no-progress-meter --header "Content-Type: application/json" \
--data "{\"name\":\"test\",\"idList\":\"${LIST}\",\"idLabels\":\"[${LABELS}]\"}" \
 "https://api.trello.com/1/cards?key=${TAK}&token=${TPT}" | jq -r '.id')

As I recall, passing a JSON array is "idLabels":"["index0","index1"]" but it has not been working for me (whether as a variable or not).
Any workarounds or correct syntax would be appreciated.

I finally found my mistake: I had the outside of the array in double-quotes.
It should be: \"idLabels\":[${LABELS}]