global class LeadPriorityClass {
     public static boolean isApexTest = false;

@future (callout=true)

public static void makePostCallout(id lid) {

 lead l = [Queries Relevant Lead Fields];
 Http http = new Http();
    HttpRequest request = new HttpRequest();
    request.setEndpoint('ENDPOINT');
    request.setMethod('POST');
    request.setHeader('Content-Type', 'application/json;charset=UTF-8');
 //set Payload Variables

 string payload = // Payload generation


    request.setBody(payload);
    system.debug('Payload: '+payload);
  //Set credentials
        String username = 'XXX';
        String password = 'XXX';

        Blob headerValue = Blob.valueOf(username + ':' + password);
        String authorizationHeader = 'BASIC '+EncodingUtil.base64Encode(headerValue);
        request.setHeader('Authorization',authorizationHeader);

HttpResponse response = http.send(request);

    // Parse the JSON response

    if (response.getStatusCode() != 200) {
        System.debug('The status code returned was not expected: ' +
            response.getStatusCode() + ' ' + response.getStatus());
    } else {
        decimal Pf = null;
        System.debug(response.getBody());
        JSONParser parser = JSON.createParser(response.getBody());
        while (parser.nextToken() != null){
            if ((parser.getCurrentToken() == JSONToken.Field_name)){
                string fieldName = parser.getText();
                parser.nextToken();
                    if(fieldName == 'probability_1'){
                        fieldName = parser.gettext();
                        system.debug('Prob: '+fieldName);
                        pf = decimal.valueOf(fieldname);
                        l.pscore__c = pf.setScale(3);
                        l.last_scored__c = datetime.now();
                    }
            }

        }
        update l;
    }
    //system.debug('Parsed: '+JSON2Apex.parse(response.getbody()));
// system.debug('Probability: ');

}