Using dynamic parameters at a request body of connector API

Using dynamic parameters at a request body of connector API

I am trying to connect ZOHO CRM with a 3rd party app. I created the connector and authorized it. I want to add any new ZOHO CRM accounts to my app directly. Request Body of API is as below:
{
  "data": {
    "id": "string",
    "type": "contacts",
    "attributes": {
      "balance": 0,
      "trl_balance": 0,
      "usd_balance": 0,
      "eur_balance": 0,
      "gbp_balance": 0,
      "created_at": "2023-05-23",
      "updated_at": "2023-05-23",
      "email": "user@example.com",
      "name": "string",
      "short_name": "string",
      "contact_type": "person",
      "tax_office": "string",
      "tax_number": "string",
      "district": "string",
      "postal_code": "string",
      "city": "string",
      "country": "string",
      "address": "string",
      "phone": "string",
      "fax": "string",
      "is_abroad": true,
      "archived": true,
      "iban": "string",
      "account_type": "customer",
      "untrackable": true,
      "invoicing_preferences": {
        "e_document_accounts": [
          0
        ]
      }
    },
    "relationships": {
      "category": {
        "data": {
          "id": "string",
          "type": "item_categories"
        }
      },
      "contact_portal": {
        "data": {
          "id": "string",
          "type": "contact_portals"
        }
      },
      "contact_people": {
        "data": [
          {
            "id": "string",
            "type": "contact_people"
          }
        ]
      }
    }
  },
  "included": [
    {
      "id": "string",
      "type": "item_categories",
      "attributes": {},
      "relationships": {}
    }
  ]
}

Only the "name" and "account type" are compulsory fields. I am using POST action to add the new customer however I am receiving an error like ({"errors":[{"title":"Bad Request","detail":"parameter -\u003e data must be a JSON Object"}]})

How should I POST the request?