Custom Function Types available - Custom Test Data and Custom Test Step : Help Center

import org.apache.commons.lang3.RandomStringUtils;
import com.testsigma.customfunc.common.TestsigmaCustomFunctions;
import com.testsigma.customfunc.common.CustomTestData;

public class RandomNumber extends 
TestsigmaCustomFunctions{
    @CustomTestData
    public String numberOfNDigits(int n){
       String randomdigits;
       //your code starts here
       ---
       ---
       ---
       //your code ends here
       return randomdigits;
    }
}

Notice that the @CustomTestData annotation is added for the Custom Function method and the return type of the method is 'String'.

As an example, you can use the above created Custom Test Data in the NLP - "Enter test data in ui identifier field" as:
Enter !|CustomRandomPhoneNumer| in ui identifier field

How to use Default Test Data Functions in Test Steps?

Custom Test Step

It is used to perform complex and AUT/SUT specific actions that are currently not available in the NLP Grammar.

Although we update the NLP Grammar library quite frequently to add all generally possible user requirements, there might be cases when a user application needs to do certain actions that are specific to them. Custom Function Test Steps provide a solution in these scenarios.

import com.testsigma.customfunc.common.TestsigmaCustomFunctions;

public class createAlert extends TestsigmaCustomFunctions{
     TestStepResult result = new TestStepResult();

      @CustomTestStep
      public String numberOfNDigits(int n){
           //your code starts here
           ---
           ---
           ---
          //your code ends here
          return result;
      }
}