Exception not returning right vars

General
1

Hi
This is my code

/**
* @param {String} from
* @param {String} to
* @param {String} u
* @param {String} t
* @returns {Promise.<Array.<ShoppingItem>>}
*/
getRatings(from, to, u, t) {
if(!from || !to || !u) {
return "Please provide mandatory fields";
}


}
but while passing string value to the API i am getting following error 
{
"code": 14004,
"message": "Service invocation failed: ExceptionClass:\"JsonMappingException\" {Msg:\"Unrecognized token 'hello1': was expecting ('true', 'false' or 'null')\n at [Source: [true,hello1,hello2,null]; line: 1, column: 13] (through reference chain: Object[][1])\", Cause:\"Unrecognized token 'hello1': was expecting ('true', 'false' or 'null')\n at [Source: [true,hello1,hello2,null]; line: 1, column: 13]\"}"
}
What am I doing wrong??? Thanks for your help

Update: I found out that if I enter “null” in each variable I get a 200 response. Great!
Now, could error message be a bit more explicit? and aligned with the issue at hand?

2

Hello!

I assume that the code you’ve showed is a part of your custom service. Can you please show the request you make to invoke this method?
Thank you!
Alex

3

This is the method: https://develop.backendless.com/swaggerui/index.html#!/Methods/getRatings

4

Provide your application id please.