"ID"                   Number
"Email"                EmailAddress  254
"LanguageID"           Locale          5
"Unsubscribed"         Boolean
"Promotion code sent"  Boolean
"T_OptedIn"            Boolean

"ID"                   "415111"
"Email"                "sampleEmail@somedomain.com"
"LanguageID"           "hu-HU"
"Unsubscribed"         "False"
"Promotion code sent"  "False"
"T_OptedIn"            "False"

{
    "contactKey": "sampleEmail@somedomain.com",
    "attributeSets": [{
        "name": "Email Addresses",
        "items": [{
            "values": [{
                "name": "Email Address",
                "value": "sampleEmail@somedomain.com"
            },
            {
                "name": "HTML Enabled",
                "value": true
            }]
        }]
    }]
}

curl -X POST --header "Content-Type:application/json" --header "Authorization: Bearer {{MY_TOKEN}}" -d "{"contactKey":"sampleEmail@somedomain.com","attributeSets":[{"name":"Email Addresses","items":[{"values":[{"name":"Email Address","value":"sampleEmail@somedomain.com"},{"name":"HTML Enabled","value":"true"}]}]}]}" "https://www.exacttargetapis.com/contacts/v1/contacts"

Host: https://www.exacttargetapis.com
POST /contacts/v1/contacts
Content-Type: application/json
Authorization: Bearer {{MY_TOKEN}}

{
    "contactKey": "sampleEmail@somedomain.com",
    "attributeSets": [{
        "name": "Email Addresses",
        "items": [{
            "values": [{
                "name": "Email Address",
                "value": "sampleEmail@somedomain.com"
            },
            {
                "name": "HTML Enabled",
                "value": true
            }]
        }]
    }]
}

{
  "operationStatus": "FAIL",
  "rowsAffected": 0,
  "requestServiceMessageID": "36f006b9-c6e0-4d8f-8907-e8ef785f0a9f",
  hasErrors": true,
  "resultMessages": [{
      "formatStringParams": [
        "ValueDefinition",
        null,
        null,
        "HTML Enabled"
      ],
      "messageFormatString": "Unable to resolve schema element of type: {0} by reference. [Id: {1}, Key: {2}, Name: {3}]",
      "resultType": "Validation",
      "resultClass": "Error",
      "resultCode": "SchemaObjectNotFoundByReference",
      "message": "Unable to resolve schema element of type: ValueDefinition by reference. [Id: , Key: , Name: HTML Enabled]"
    }],
  "serviceMessageID": "b1c2fbe6-1a95-4802-b838-1ff817ea08eb"
}