Creating “The Functionality” Part 1: Introduction and “Existing Functionality”

In the post with the overall description with the magic formula for Skills, we broke those down in two parts: The Interaction Model and “The Functionality”. My usage of quotation marks is not just for fun. In the documentation provided by Amazon, the interaction model is mentioned by name all the time. The other part, no. So I decided to coin the term myself. Any kind readers with a better suggestion please leave it in the comments!

So, it’s now time to discuss “the Functionality”. This is what I’ve already said about the matter:

“The functionality” can be an application that already exists (Fitbit, Uber, etc. were happy systems with millions of users before Alexa was invented), or one you make now to be used specifically with Alexa. In the first case, the developers for that existing system will have to develop an interface that uses the AVS API. Well, actually, a product manager will have to identify the functionality that will be used via Alexa, then the developers will encapsulate that functionality in a way that can be exposed to the AVS API so that Alexa can use it. In some cases the developer and the product manager are the same person!

If you’re creating a Skill from scratch, then Amazon recommends that you build and host “the functionality” with Amazon Web Services and they suggest you do it as a Lambda Function. We’ll speak a lot about this soon, stay tuned!


I don’t know if it was clear enough, so here it goes. “The Functionality” is the stuff that the Skill actually does (telling the time, the horoscope, telling you the status of a flight, telling you how to prepare a mojito, suggesting which wines go well with pasta, etc.) And of course this functionality can already exist and is currently used through a different format (smartphone app, Web application, wearable, plain old desktop application, etc.) or you can create something totally new.

Existing functionality: Focus is Key

This will be the most frequent case. Your bank decides to offer their services to Alexa. Your fitness tracker expands the way to interact with you with voice.  And a long et cetera. Every month new Skills with existing functionality are published in the Alexa Skills list.

So, how does it work? You already have a working system with zillions of users. How do you add it to the list of stuff that Alexa is capable of doing? Well, first of all you need to define what functionality you want to expose to Alexa (“expose” here means “make available to”). Imagine you’re a bank. What do you want your customers to be able to do with voice? You have to get a lot of things into consideration. Stuff that is different with voice than with other interfaces. This list is not exhaustive:

  • Security & Privacy considerations: anyone in the house can give instructions to Alexa. It’s probably not a good idea to be able to do bank transfers via voice. And everyone around will hear what Alexa says. Is it okay to hear your account balance? Don’t even think of protecting transactions with passwords. Because the point of Alexa with many user personas is that they can only use voice, and the possibility of eavesdropping makes saying passwords aloud a no-no.
  • Ergonomy: Okay, this is the realm of the Voice Interaction Designer, but  you really need her input to decide what will fly and what will never work. Imagine you want to interact with your fitness tracker via Alexa. Will there be any value in hearing the list of your heart rates minute by minute? Will you remember it, will you aprehend it? The amount of information that a human can process depends on the sense being used. Sight is okay for browsing and for finding a needle of information in a visual haystack. Hearing is not.
  • Value and coherence: You want to implement stuff that is useful to the user and that brings value to your organization. And you want to paint a coherent picture to your user. He or she should not get frustrated because things you’ve implemented lead her to believe that similar or related things, ones that seem equally important to the user, are also implemented, when they are not.

Sounds daunting? No, not really. It’s just a lot of work. This is why you need a Product Owner, or you need to be able to act like one and devote enough time to it, when designing any kind of system. You need someone who knows well the needs of the organization, the needs of the user and who is capable of understanding the possibilities and limitations of the technologies being used.

Okay, imagine you’ve done all of that and you have a list of “services” you want to use through Alexa Voice Services. What do you have to do now? Easy. Get your Developer and your Interaction Designer together, get them together, make them read and understand the post about the Interaction Model (probably they know much more than me, so maybe they skip this part!), make them agree the “contract” between Functionality and Interaction Model (the Intent Schema) (don’t let them part ways until they do this!!)

Technical Implementation

Now your Developer can start work. It’s all about creating a Web service that exposes the functionality that you wish to serve via Alexa. Remember this diagram? It’s the bit at the bottom right.

AVS Overview
AVS Overview – “The Functionality” depicted on the bottom right part of the diagram.

Your Web Service must comply with the following (extracted from here. My comments between [square brackets]):

  1. The service must be Internet-accessible. [Pretty obvious, eh! But not easy to achieve in some big organizations.]
  2. The service must adhere to the Alexa Skills Kit interface. [More on it later]
  3. The service must support HTTP over SSL/TLS, leveraging an Amazon-trusted certificate.
    • For testing, Amazon accepts different methods for providing a certificate. [i.e. you don’t have to shell out money buying a certificate when you’re just testing]. For details, see the “About the SSL Options” section of Registering and Managing Custom Skills in the Developer Portal.
    • For publishing to end users, Amazon only trusts certificates that have been signed by an Amazon-approved certificate authority. [You work with Amazon, you leverage their services, you accept their rules. Certificates are a matter of trust anyways and you should use the ones they trust!]
  4. The service must accept requests on port 443.
  5. The service must present a certificate with a subject alternate name that matches the domain name of the endpoint.
  6. The service must validate that incoming requests are coming from Alexa. [This last point is actually trying to protect you from DoS attacks]

So, the secret of the sauce is in complying with the Alexa Skills kit interface. And believe me, this will be trite unless you understand how the custom skill works, what you need to do to react to Intents, how to handle slots, and so on. To do that, you need to understand very well the interface specification but most important perhaps, have a broad picture of how everything clicks together. To do that, I recommend two things:

This will be time well spent, it will pay off with a high return rate later.

Good luck!

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