#1255: Incubation: Application Capability

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Opened Aug 6, 2026

Explainer

https://dokieli.github.io/application-capability/

The explainer

Where and by whom is the work is being done?

Feedback so far

  • Multi-stakeholder feedback:
    • Chromium comments: N/A (not requested; see note below)
    • Mozilla comments: N/A (not requested; see note below)
    • WebKit comments: N/A (not requested; see note below)
    • Developer and implementer feedback:
    • Note: the specification requires no browser engine changes. Discovery is dereferencing a description, and invocation is ordinary navigation to an IRI, so we have not requested engine vendor positions. We'd still welcome their review, particularly from those working on agent and application interoperability (for example WebMCP, see also https://github.com/w3ctag/design-reviews/issues/1238 ).
  • Major unresolved issues with or opposition to this design:
    • Venue: which existing or new standards group should further develop this specification (the question we are asking the TAG).
    • The JSON-LD context and vocabulary are included in the specification until published at their own namespace.
    • Under consideration: declaring whether an action has side effects (with guidance for Consumers acting autonomously), and describing capabilities of applications beyond the web, such as PWA and desktop applications.
    • Would like to: do user research =)

You should also know that...

TAG hat off =)

Appreciate your time and consideration on this work.

@marcoscaceres recommended that we create this design review request.

Please note that the Explainer is a section in the specification.

From the TAG, we would like direction on venue. In which existing standards group, or under what new group, should this specification be further developed? And, needless to say, any other direction would be great.

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Track conversations at https://tag-github-bot.w3.org/gh/w3ctag/design-reviews/1255

Discussions

Discussed Aug 10, 2026 (See Github)

Sarven: There is an explainer in the repo. As the name implies, this is a structured way for apps to publish their capabilities, requirements, and policies which can be used by other apps, servers, or user agents. Publishing means, as a standalone resource, incorporated into the Web Application Manifest, or other ways, so the app itself or other users can make decisions based on that information, i.e., what an app needs or what it’s about to do.

… One point is permissions. Today, servers might set a security policy which applies to all services there. With this approach, this information is declarative and accessible as a resource, so consumers can query it. In that way, servers can make application/resource specific decisions. Same problems have been solved in other parts of the web and operating systems, e.g., file handling.

… Some of the features of the spec allows users to choose the right applications. Also, potentially overlapping use cases with WebMCP. Contrast is that it’s purely declarative.

Heather: So your ask is to check where this should go from here?

Sarven: Yes, discussed it in SOLID CG, but the question was if there’s wider interest or another group that could take over this work, or whether a new group should be created.

Lola: What about the WebApps WG? This seems aligned with their goals.

Heather: Exploration IG was founded exactly for that.

Marcos: This is great because it covers similar grounds than WebMCP, allows you to do the same things. In WebApps it would have go through the entire incubation process. Sounds very interesting.

Brian: +1 to what Heather said. The non-goal is script-level tool calling. Rationale for WebMCP for choosing that is to extend existing applications vs. rethinking them from the ground up. Curious where this belongs in the spectrum of web services.

Sarven: It’s also about how to invoke ??? in the application.

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Comment by @hlflanagan Aug 14, 2026 (See Github)

Thank you for bringing this to the TAG. We recommend taking the idea to the Exploration IG as a next step, where it can be discussed further and the appropriate venue for the work can be identified.

We also recommend coordinating with the WebMCP work and making sure that group is aware of this proposal, since there may be overlap between the two efforts or this approach may provide an alternative worth considering.

Comment by @csarven Aug 18, 2026 (See Github)

TAG meeting minutes for this topic: https://github.com/w3ctag/meetings/blob/gh-pages/2026/telcons/08-10-minutes.md#incubation-application-capability

Comment by @csarven Aug 18, 2026 (See Github)

Following up at Exploration IG: