Digital Assistant provides a set of components that support a range of generic actions, which you can use in any skill: security, parsing the user input, routing the dialog flow based on that user input, and outputting the skill’s responses in various ways. Unless you need to integrate with backends or perform extremely complex logic, these components will provide the actions that your states need.

The way you access components depends on whether you are designing the dialog flow with the Visual Flow Designer or in YAML mode:

• If you are using the Visual Flow Designer, you add the first state for a built-in component to a flow by hovering over its Start tile, clicking the menu , selecting Add start state, and then selecting a component template from the Add State dialog. You can add subsequent states by selecting Add state from a state's menu or by clicking the Add a state to this transition icon between two states. See Designing Flows.
• If you are designing your skill in YAML mode, you add a state for a built-in component to your dialog flow by selecting + Components and then selecting a component template from the menu.

When you validate your dialog flow, Digital Assistant verifies the component's properties. For example, it will report if you forgot to include a required property.

For details on the component templates available in the Visual Flow Designer, see Component Templates

For details on components available in YAML mode, see Built-In Components: Properties, Transitions, and Usage.

Most skills need to integrate with data from remote systems or do some backend processing. For example, your skill might need to get a list of products or save order information. Another example is that your skill might need to perform complex logic that you can't accomplish using FreeMarker or an entity event handler. Custom components enable you to integrate with backends as well as perform tasks that aren't covered by the built-in components.

To learn how to build a custom component, see Implement Custom Components. To learn how to add custom components for use in your skill, see Add Component Package to a Skill. To learn about a custom component that's been added to the skill, go to the skill's Components page, expand the component service and select the component. The component's name, properties and supported actions are displayed. Use this information to build the component's state in your dialog flow.

Here's an example of a custom component state in a dialog flow that is developed in YAML mode. The hello.world component is from the custom service.

  start:
    component: "custom:helloWorld"
    properties:
      human: "${human.value}"
    transitions:
      next: "askAge"

When you use the embedded component service to host your custom components, you can access view logs and crash reports for the components from the Components page. Select the service, and then click Diagnostics.