How to Calculate Service Area based on walking time ?

I'd like to calculate service areas based on walking time :

For now, I tried two things : with a url+parameters and with the Attributes Parameter Values

So, for the first case, I have this URL :

https://route.arcgis.com/arcgis/rest/services/World/ServiceAreas/NAServer/ServiceArea_World/solveServiceArea?travelMode={"attributeParameterValues":[{"parameterName":"Restriction Usage","attributeName":"Walking",

"value":"PROHIBITED"},{"parameterName":"Restriction Usage","attributeName":"Preferred for Pedestrians",

"value":"PREFER_LOW"},{"parameterName":"Walking Speed (km/h)","attributeName":"WalkTime","value":5}],

"description":"Follows paths and roads that allow pedestrian traffic and finds solutions that optimize travel time. The walking speed is set to 5 kilometers per hour.",

"impedanceAttributeName":"WalkTime","simplificationToleranceUnits":"esriMeters",

"uturnAtJunctions":"esriNFSBAllowBacktrack","restrictionAttributeNames":["Preferred for Pedestrians","Walking"],

"useHierarchy":false,"simplificationTolerance":2,"timeAttributeName":"WalkTime",

"distanceAttributeName":"Miles","type":"WALK","id":"caFAgoThrvUpkFBW","name":"Walking Time"}&token=" +$webRequest1.text

My second attempt, by setting Attribute Parameter Values to :

=[{

      "parameterName": "Restriction Usage",

      "attributeName": "Walking",

      "value": "PROHIBITED"

   }, {

      "parameterName": "Restriction Usage",

      "attributeName": "Preferred for Pedestrians",

      "value": "PREFER_LOW"

   }, {

      "parameterName": "Walking Speed (km/h)",

      "attributeName": "WalkTime",

      "value": 5

   }]

I don't know what I am doing wrong.

So if someone here has solved this problem, plz tell me !

Thx !