AWS API Gateway: {"message":"Not Found"}

Question

I'm trying out AWS API Gateway for the first time, using HTTP Gateway as the gateway style and Lambda as the execution method. My Lambda function requires no input, and outputs a number. This has been confirmed using the Test button. But then I configure the Gateway to use this function, and it gives me an invoke URL. I click the URL, and what comes back is {"message":"Not Found"}.

Can anyone give me a clue where to look? I am wondering, what sort of object at what level was not found?

(I did not use the Deploy button on the API's page, because that looks like a deeper level of complexity only needed if one is going to employ more versions or configurations.)

The function is configured to use lambda_function.second as the entry point, and this has been tested within Lambda. Here's the relevant code:

import logging

logger = logging.getLogger()
logger.setLevel(logging.INFO)

def second(event, context):
    ...
    result = None
    action = 'increment'
    number = event.get('number', 17)
    if action == 'increment':
        result = number + 1
        logger.info('Calculated result of %s', result)
    else:
        logger.error("%s is not a valid action.", action)

    response = {'result': result}
    return response

Answer 1

Turns out that the URL provided on the API Gateway page may not be complete. They gave me

https://js6g8a6b3l.execute-api.us-east-2.amazonaws.com

But then there are also routes. And I had defined only one route, named incrementTest. So the correct URL was in fact

https://js6g8a6b3l.execute-api.us-east-2.amazonaws.com/incrementTest