question

A good first step would be to check the card in your Alexa app. It sometimes shows more information than the audio output.

Built-in intents are designed to be used the exact same way as custom intents. You can include them in your Intent Schema and reference them in your Lambda function. The primary benefit of using built-in intents is that you do not need to include Sample Utterances to use them. More information on built-in intents can be found here: https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/implementing-the-built-in-intents. Logs generated from your Lambda function can be viewed through the AWS console by using CloudWatch. When debugging your skills they can be quite useful at providing more insight than the cards in the Amazon Alexa application.