Interpreting a JSON Response in HTTP XML/Rest Value sensor

I've got the free version of PRTG running at home, and I've also got quite a few Hue lights, and I was interested in seeing if I could keep tabs of the reachability of the Hue bulbs - for fun, just to try out the possibilities.

The API call to look up a specific light status is as follows:

http://192.168.0.111/api/77DiCq1MBnwE4W9IbIoVonQ65moMIseEuw6ui-sB/lights/10

And this is the JSON response.

{
"state": {
"on": true,
"bri": 254,
"hue": 14956,
"sat": 140,
"effect": "none",
"xy": [
  0.4571,
  0.4097
],
"ct": 366,
"alert": "none",
"colormode": "ct",
"reachable": true
},
"type": "Extended color light",
"name": "Bonus Room Desk",
"modelid": "LCT007",
"manufacturername": "Philips",
"uniqueid": "00:17:88:01:10:5a:79:90-0b",
"swversion": "5.50.1.19085"
}

I was using the HTTP XML/Rest Value sensor to try and test the result - I'd rather not have to write a custom sensor for this. Unfortunately, while I can point at the value for "reachable" with "state/reachable" in the XML Node, I'm not sure how to determine whether the value is "true" or "false".

Ideas?

http json rest