Returning value from ArcGIS Pro custom tool (.py)

How do we return a value from a custom .py tool, so that when I run the tool in another script, it will return a value (such as a number, string, or tuple)?

Notice in the execute class function, I attempt to return a tuple of values (trying both arcpy.SetParameter and return). However, when I run the tool in a separate script, the return value is None.

I use the following code to import the toolbox and run the code:

arcpy.ImportToolbox(pyt_path, "myToolbox")
result = arcpy.myToolbox.HelloWorld()

Below is an example .py script for the tool above

import arcpy

class HelloWorld(object):
    def __init__(self):
        """Define the tool (tool name is the name of the class)."""
        self.label = "Hello World"
        self.description = ""
        self.canRunInBackground = False

    def getParameterInfo(self):
        
        """Define parameter definitions"""
        param1 = arcpy.Parameter(
            displayName="output",
            name="outparam",
            datatype="GPString",
            parameterType="Derived",
            direction="Output")

        return [param1]

    def isLicensed(self):
        """Set whether tool is licensed to execute."""
        return True

    def updateParameters(self, parameters):
        """Modify the values and properties of parameters before internal
        validation is performed.  This method is called whenever a parameter
        has been changed."""
        return

    def updateMessages(self, parameters):
        """Modify the messages created by internal validation for each tool
        parameter.  This method is called after internal validation."""
        return

    def execute(self, parameters, messages):
        """The source code of the tool."""      
        arcpy.AddMessage("Hello World!")
        arcpy.SetParameter(0, "Hello world")
        return "Hello world"

    def postExecute(self, parameters):
        """This method takes place after outputs are processed and
        added to the display."""
        return

Below is my .pyt file

from HelloWorld import HelloWorld

class Toolbox(object):

    def __init__(self):
        """Define the toolbox (the name of the toolbox is the name of the .pyt file)."""
        self.label = 'Test TBX'
        self.alias = 'TestTBX'

        # List of Tool classes associated with this toolbox
        self.tools = [HelloWorld]

Here is a regular arcpy example using their Spatial Analyst toolbox. I would like to get a return value as well with my custom tool.

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import Basin

# Set environment settings
env.workspace = "C:/Path/To/Data"

# Set local variables
inFlowDirectionRaster = "flowdir"

# Execute FlowDirection
outBasin = Basin(inFlowDirectionRaster)