in_header data in json requests

[solartune]

Hi guys! I don't understand, how can I send header data in json request?
In soap request I just do this

<soapenv:Header>
      <soap:headerData>
        <soap:data>my_data</soap:data>
      </soap:headerData>
   </soapenv:Header>

But in json request I can't do the same. When I try to do something like this

{
    "headerData": {
	"data": "my_data"
    },
    "getEmployee": {
	"number": "employee_number"
    }
}

I get the next error:

{
    "faultcode": "Client.ValidationError",
    "faultstring": "The value \"'Need a dictionary with exactly one key as method name.'\" could not be validated."
}

Thanks.