WebMCP: JavaScript tools exposed by a page
Study the experimental API and the exact status of the community draft.
What WebMCP proposes
WebMCP proposes a JavaScript interface for pages to expose functions as callable tools for agents. Natural language descriptions and structured input schemas help discover features normally activated by users.
Status as of 13 November 2026
The Web Machine Learning Community Group report remains a community draft rather than a W3C Recommendation. The imperative API is documented; a declarative approach built around HTML forms is explored separately and must not be described as universally implemented.
User-interface control
Exposed tools should describe expected effects and honor the page’s authorization context. A function available in JavaScript is not automatically authorized to run without human consent.
Experimental prototype
Start with a reversible operation such as a search filter, then verify browser support. Do not imply that a live agent is available when the example only demonstrates a schema or simulation.
Community status and exposed functions
The proposed imperative WebMCP API explores how pages declare functions callable by agents. The Community Group report is not a W3C Recommendation and browser availability needs checking. Input schemas help describe parameters but do not replace execution authorization or application safeguards.
Exercise: side-effect-free navigation function
Describe a function opening a course page from an allowed identifier. Check malformed parameters produce understandable errors and the HTML UI remains keyboard accessible. In a demo, distinguish conceptual descriptions from actually supported APIs; do not claim an external agent is connected when no real invocation occurs.
Core steps
- 01Read the community draft
- 02Model a harmless action
- 03Check actual browser support
- 04Review permission boundaries
Three questions to ask
Is this an adopted W3C Recommendation?
Is the declarative form API part of the current core?
Is the exposed action actually authorized?
Read the source documents
Versions, reuse terms and document status can change. Check them on the original sites.