Create Custom Field

{
  "name": "Department",
  "field_type": "SINGLE_LINE_TEXT",
  "entity_type": "CONTACT"
}

{
  "name": "Priority Level",
  "field_type": "SINGLE_SELECT",
  "entity_type": "CONTACT",
  "multi_select_options": [
    "High",
    "Medium",
    "Low",
    {
      "value": "Critical"
    }
  ]
}

{
  "name": "Technologies",
  "field_type": "MULTI_SELECT",
  "entity_type": "COMPANY",
  "multi_select_options": [
    "JavaScript",
    "Python",
    "React",
    "Node.js",
    {
      "value": "TypeScript"
    }
  ]
}

{
  "data": {
    "id": "field_99999",
    "name": "Priority Level",
    "field_type": "SINGLE_SELECT",
    "entity_type": "CONTACT",
    "created_at": "2025-01-15T10:30:00Z",
    "updated_at": "2025-01-15T10:30:00Z",
    "multi_select_options": [
      {
        "id": "option_301",
        "value": "Critical"
      },
      {
        "id": "option_302",
        "value": "High"
      },
      {
        "id": "option_303",
        "value": "Low"
      },
      {
        "id": "option_304",
        "value": "Medium"
      }
    ]
  }
}

{
  "data": {
    "id": "field_88888",
    "name": "Department",
    "field_type": "SINGLE_LINE_TEXT",
    "entity_type": "CONTACT",
    "created_at": "2025-01-15T10:30:00Z",
    "updated_at": "2025-01-15T10:30:00Z"
  }
}