I am writing an apex button to invoke a class and am recieving the following error:

A problem with the OnClick JavaScript for this button or link was encountered:

{faultcode:'soapenv:Client', faultstring:'No operation available for request {http://soap.sforce.com/schemas/package/ProductDescription}SplitDescription, please check the WSDL for the service.', }

The apex class and the javascript have the same class.

Button:

// Include and initialize the AJAX toolkit library
{!REQUIRESCRIPT("/soap/ajax/26.0/connection.js")};
{!REQUIRESCRIPT("/soap/ajax/26.0/apex.js")};
var idList = {!GETRECORDIDS($ObjectType.QuoteLineItem)};
var retURL = window.location.toString();
var proceed = true;
if(idList.length == 0){
alert('Please select at least 1 record.');
proceed = false;
}
if(idList.length != 0){
var myvar = sforce.apex.execute("ProductDescription","SplitDescription",{QuotteLinetem_id:idList})
window.alert(myvar);

}

 Class un version 26.0

Global class ProductDescription {
    

    List<String> xarray = new List<String>();
    QuoteLineItem qli {get; set;}
    id idlist;
    
    public ProductDescription(ApexPages.StandardController c) {
        qli = [select id from Quotelineitem where id =: ApexPages.currentpage().getParameters().get('qli')];
        system.debug('###########qli:'+qli);
    }

   Public pageReference SplitDescription(){
   
   List<QuoteLineItem> cqli = [select id, pricebookentryid, PricebookEntry.Product2.Description
                                   from QuoteLineItem where id =:idList];

   For(Quotelineitem qli : cqli){
     xarray = qli.PricebookEntry.Product2.Description.split('\n');   
        system.debug(xarray);
   }
    Product_Description_Line__c[] split = new Product_Description_Line__c[0];
    For(String sa : xarray){
           split.add(New Product_Description_Line__c(quote__c = cqli[0].quoteid,
                    Quote_Line_Item__c = cqli[0].id,
                    Description_Line__c = sa
                    ));

   insert split;

  }
  return null;
  }
}

 What am I doing wrong and how do I solve the error?

Thank you