Alexa developers can now charge users for “premium digital content to enrich [an] Alexa skill experience,” Amazon announced today, as the company has rolled out “in-skill purchasing (ISP)” for Alexa skills to all developers building skills for United States customers. The feature was previously available in a handful of titles.

Amazon says that Alexa skills will continue to be free for customers, enabling them to assess each skill’s quality and features before making a purchase. But ISPs will enable developers to offer one-time purchases of features or content, as well as subscriptions that grant access to features or content over time. Consumables — such as in-game hints that disappear after each use — are not currently supported.

In-skill purchasing can already be found in Jeopardy games, The Ellen Show’s Heads Up, and TuneIn’s Live audio service, as well as a couple of other Alexa skills. As of today, SyFy Wire is adding subscription-based access to exclusive weekly podcasts, and the game Yes Sire is adding an expansion pack.

For customers, the feature will be pretty much like using Alexa to make Amazon purchases: Voice commands will be able to trigger purchases using payment options linked to their Amazon accounts. Developers will supply the list of offerings and prices, receiving a 70 percent cut of the list price before any discount offered by Amazon itself.

Amazon has also posted a best practices guide to “designing premium experiences for Alexa skills,” noting that the one-time purchases are designed to be “enduring entitlements” that should be easy to find in the skill, but marketed as a “solution, not a sales pitch.” The retailer already offers a separate Alexa Developer Rewards¬†program enabling developers to sell real-world products, such as ordering food, and services, such as booking a ride.