Trouble populating text field widget while executing node.create through Service using Rest server
Field values need to be surrounded by an array, which holds all the potentially multiple entries for the field, and yet another array which holds all of the potential translations for the field.

In PHP that looks something like this:

$node-&gt;field_text['und'][0]['value'] = 'Some Text';


I haven't tested it but I'd guess the JSON equivalent would be something like this:

"field_text":
{
  "und": 
  [
    { "value": "Some Text" }
  ]
}


That may need a bit of tweaking.