Add Custom Capabilities with the Smart Home AI Toolkit
A custom capability defines a device feature that pre-built Alexa interfaces don't cover. You create the custom capability and add it to a device that represents your physical product. You can combine custom capabilities with pre-built Alexa interfaces on the same device to fully represent your product features to Alexa.
The Smart Home AI Toolkit guides you through this process using AI-assisted development. You chat with the Alexa+ smart home agent to define your capability. The agent generates the interface definition (directives, properties, and responses) and test utterances, saves your capability to a device, and generates a device control UI for the Alexa app and Alexa-enabled devices with a screen. You instruct the agent where to make changes.
After you complete the capability definition, you include it in your smart home add-on, following the same process you use for pre-built Alexa interfaces. When a customer uses your device, Alexa+ infers the correct capability from customer utterances.
At this time, you can create custom capabilities in English (US) only.
Choose your starting point
The Smart Home AI Toolkit provides two starting points. Both lead to the same review, testing, and submission steps.
- Chat and Build – A guided conversational flow with the Alexa+ smart home agent. Choose this option when you want to describe your device in plain language and let the agent ask clarifying questions. This method doesn't require technical knowledge and is the recommended starting point.
- Upload Specification – A document-driven flow. Choose this option when you have formal technical documentation, such as requirements, an API reference, or a JSON manifest file. Here, the agent extracts as much information as possible automatically, and then asks about gaps.
Model capabilities
Each capability defines the actions, properties, and responses for a specific device feature. You build individual capabilities and add them to a device, which represents your physical product. The device includes the custom and pre-built capability interfaces that match the features of your product. The Alexa+ smart home agent generates sample voice utterances and a device control UI for the capabilities you include. After you finish adding capabilities to your device, you test and publish the device for review.
Consider a pet feeder with two features: fill the food and water bowls, and turn the feeder on and off. You might build a custom capability to fill the food and water bowls and also use the pre-built Alexa.PowerController capability to turn on the feeder. You combine these capabilities into your pet feeder device and publish the device for review. After Amazon completes the review, Alexa+ can route customer utterances to the correct capability on your device.
Steps to build custom capabilities
Complete the following steps to add custom capabilities for your device.
- Build custom capabilities.
- Test custom capabilities.
- Publish a device with custom capabilities. Amazon reviews and approves your custom capabilities.
- Include the custom capabilities in your smart home add-on. You follow the same process you use for pre-built Alexa interfaces.
Best practices
Follow these best practices to create a custom capability interface.
- Use natural language descriptions. Describe your device capabilities conversationally in English. The agent interprets natural language more effectively than cryptic names or shorthand. For example, describe an action as "Fill the pet's food bowl" rather than "fillBowl."
- Provide high-quality action descriptions. These descriptions help Alexa+ identify the correct interface for a customer utterance.
- Support multiple property formats. Make sure that the properties support customers in different locations. For example, for temperature, best practice is to support both Fahrenheit and Celsius.
- Verify the generated utterances. The accuracy of the generated custom capability depends on how well the sample utterances reflect real-world language. Make sure that the generated utterances sound natural and cover the ways customers are likely to phrase requests to Alexa.
- Report state changes. If your capability defines reportable properties, report state changes to Alexa. For more details, see Understand State and Change Reporting.
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Last updated: Aug 01, 2026
