Sending to Google sheets from Android device via Google Script. Is this secure?

I followed this tutorial: https://www.crazycodersclub.com/android/how-to-use-google-sheet-as-database-for-android-app-1-insert-operation/

Somehow, I got it working for androidX. I want to send sensitive location information over the air to my Google sheet link. How secure is this? I have used OAuth2 with gspread in Python before, and relied on a .json key. This seems so much easier... Can users discover my link and read my private entries? Or is there some limitation where they can only send data to the sheet?

Web app code:

var ss = SpreadsheetApp.openByUrl("Add Your Spread Sheet URL here");

var sheet = ss.getSheetByName('Items'); // be very careful ... it is the sheet name .. so it should match 


function doPost(e){
var action = e.parameter.action;

if(action == 'addItem'){
  return addItem(e);

}

}





function addItem(e){

var date =  new Date();

var id  =  "Item"+sheet.getLastRow(); // Item1

var itemName = e.parameter.itemName;

var brand = e.parameter.brand;

sheet.appendRow([date,id,itemName,brand]);

   return ContentService.createTextOutput("Success").setMimeType(ContentService.MimeType.TEXT);



}

My sheet is set to be viewable only by me. The webapp is deployed as everyone has access even anonymous

this is how it's called in the android app:

StringRequest stringRequest = new StringRequest(Request.Method.POST, "Add Your Web App URL",
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {

                loading.dismiss();
                Toast.makeText(AddItem.this,response,Toast.LENGTH_LONG).show();
                Intent intent = new Intent(getApplicationContext(),MainActivity.class);
                startActivity(intent);

            }
        },
        new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        }