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July 22, 2016Zoey Collier
In our first post, we shared why Discovery decided to build an Alexa skill and what requirements they outlined as they thought through what the voice experience should look like. In this post, we’ll share how they built and tested their Alexa skill and their tips for other Alexa developers.
When Stephen Garlick, Lead Development and Operations Engineer at Discovery Channel, took the lead in developing the Alexa skill, it was a chance to learn how to design a new experience for customers. He had no prior experience with AWS Lambda and Alexa Skills Kit (ASK). To start, he spent some time digging into online technical documentation and code samples provided on the Alexa Github repo. This helped him gain a deeper understanding of how to build the foundation of the Alexa skill and handle basic tasks.
By using AWS Lambda and ASK, Stephen and team were able to keep things simple and quickly deploy the code without the need to set up additional infrastructure to support the skill. Additionally, they were easily able to extend the node.js skill without having to create a skill from scratch.
Initially, Discovery used Alexa to respond with facts; later, they decided to customize her voice by using a mp3 playback. To accomplish this, Stephen used the SSML support for mp3 playback and AWS S3 with cloud front for hosting the files reliably. Each mp3 was less than 90 seconds in length, 48 kbps, and adhered to MPEG version 2 specifications. All the resources were created and deployed using the AWS CloudFormation service.
For the countdown feature, Stephen pulled in the moment.js dependency into node.js to help simplify some time-based calculations. The countdown now combines a mp3 playback for everything except the actual time which is played back by Alexa.
To test the skill, they used the skill test pane within the Alexa app. The testing tool made it easy to quickly test various scenarios without an Alexa-enabled device. Once the skill was operating as expected (and desired) in the test pane, Stephen asked other people to test the Shark Week skill on Alexa-enabled devices. This allowed them to collect additional feedback and iterate accordingly.
Overall, the entire process of learning these new technologies, coding, and building the skill took no more than 12 hours. This included a few iterations of the Alexa skill as well.
Tip #1: Make The Skill As Human As Possible: Initially, Discovery had the Alexa voice state each of the randomized facts. In an attempt to assist with the pronunciation, they spelled a few of the words and numbers phonetically. However, in doing so, the cards displayed in the Alexa app weren't correct. It quickly became apparent that a recorded reading of each fact eliminated the pronunciation issues, enabled proper spelling of facts for the cards in the Alexa app, and made the entire experience more personal.
Tip #2: Plan for Time Sensitive Coding: If you're building time specific functionality (e.g.; a countdown timer to a specific time), make sure you think about what happens when the specific time arrives. The team at Discovery was able to account for the Shark Week kickoff by providing three different countdown messages based on time in each specific time zone. The first was the countdown lead in, the second was a message indicating that Shark Week already started, and the third indicated that Shark Week had concluded and that the Shark Week website provides other shark-related information year-round.
Tip #3: Control for Volume: If you're using a combination of recordings and Alexa powered speech, make sure the volume levels are consistent throughout the experience.
Tip #4: Be Creative with Your Intent Schema and Utterances: People think, act, and speak differently. Therefore, it's important that you account for as many different intents as possible. For example, after you ask for a Shark Week fact, the skill will ask if you would like to hear another. Just a few of Discovery’s "no" utterances include "no," "nope," "no thanks," "no thank you," "not really," "definitely not," "no way," "nah," negative," "no sir," "maybe another time," and many more. It's better to be as inclusive as possible, rather than having Alexa unable to understand.
Tip #5: Take Chances: Push your limits and think big when it comes to building your Alexa skill. Discovery started the project with a broad scope in mind and were able to quickly iterate and resubmit the skill for certification.
Share other innovative ways you’re using Alexa in your life. Tweet us @alexadevs with hashtag #AlexaDevStory.
Are you ready to build your first (or next) Alexa skill? Build a custom skill or use one of our easy tutorials to get started quickly.