Unable to assign position tags in POST employee

I've been trying to create a JSON post code for POST employee. Everything works fine except the position assignment tags, which doesn't post as required. The API documentation states that the positions should be an array, and I had hence typed accordingly:

{
"fname": "2DO NOT DEPLOY",
"eid": "TestAccount5",
"status": 0,
"group": 5,
"email": "[email protected]",
"cell_phone": "651-111-1111",
"custom": {
"39689": "[email protected]",
"39690": "651-111-2222",
"39685": "abc",
"39720": "Admin Support",
"39733": "2DO NOT DEPLOYIC",
"39797": "CFS",
"39869": "5TestStartDate2",
"39872": "5TestEndDate2",
"39873": "3",
"39874": ""
},
"positions": [
2423645
],
"skills": [
152048,
153018,
155334
]
}