Adding custom claim to cognito id token

I have successfully implemented a java lambda trigger to add custom claim to token generated by cognito. but when i try to add a list to the claim its fails to authenticate. as you can see from the below code. when i try to add the authorities its fails.

@Override
    public Map<String, Object> handleRequest(Map<String, Object> event, Context context) {
        LambdaLogger logger = context.getLogger();
        logger.log(event.toString());
        String username = (String) event.get("userName");
        logger.log("username ="+username);
        Map<String,Object> claimsToAddOrOverride = new HashMap<>();
        claimsToAddOrOverride.put("key-1","value-1");
        claimsToAddOrOverride.put("key-2","value-2");
        claimsToAddOrOverride.put("organization_id", UUID.randomUUID().toString());
        claimsToAddOrOverride.put("THEME","tagd");
        claimsToAddOrOverride.put("isAiBoostEnabled",true);

        List<String> auth = Arrays.asList("auth-1","auth-2","auth-3");
        claimsToAddOrOverride.put("authorities-1",auth);
        Map<String,Object> claimsOverrideDetails = new HashMap<>();
        claimsOverrideDetails.put("claimsToAddOrOverride",claimsToAddOrOverride);


        Map<String,Object> responseMap = new HashMap<>();
        responseMap.put("claimsOverrideDetails",claimsOverrideDetails);
        event.put("response",responseMap);
        logger.log("Final payload = "+event.toString());
        return event;

    }