Declarative API is not working

[Razvan Dimulescu]

Hi,

I've been experimenting with WebMCP and ran into an issue with the Declarative API that I can't resolve. Forms annotated with toolname and tooldescription attributes are not discovered or listed by the Inspector extension. 

The Imperative API works correctly. Tools registered via window.navigator.modelContext.provideContext() and registerTool() are visible in the Inspector extension and can be invoked as expected.

I've tried with some custom code written by me but also with the code from the french-bistro demo.

Environment
- Chrome 146 (confirmed via chrome://version)
- Flag enabled: chrome://flags/#enable-webmcp-testing → Enabled, Chrome fully relaunched
- Model Context Tool Inspector extension installed
- Page served over HTTP via both http-server (Node) and Vite dev server 

 

Thank you in advanced :) 

[Razvan Dimulescu]

After investigating a few more, I discovered that using provideContext tool, it overrides also declarative tools.

[François Beaufort]

On Sun, Mar 1, 2026 at 12:26 PM Razvan Dimulescu <razvan.d...@gmail.com> wrote:

After investigating a few more, I discovered that using provideContext tool, it overrides also declarative tools.

Indeed!
Note that folks are currently discussing whether provideContextshould be removed in https://github.com/webmachinelearning/webmcp/issues/101 

Il giorno sabato 28 febbraio 2026 alle 15:53:44 UTC+1 Razvan Dimulescu ha scritto:

Hi,

I've been experimenting with WebMCP and ran into an issue with the Declarative API that I can't resolve. Forms annotated with toolname and tooldescription attributes are not discovered or listed by the Inspector extension. 

The Imperative API works correctly. Tools registered via window.navigator.modelContext.provideContext() and registerTool() are visible in the Inspector extension and can be invoked as expected.

I've tried with some custom code written by me but also with the code from the french-bistro demo.

Environment
- Chrome 146 (confirmed via chrome://version)
- Flag enabled: chrome://flags/#enable-webmcp-testing → Enabled, Chrome fully relaunched
- Model Context Tool Inspector extension installed
- Page served over HTTP via both http-server (Node) and Vite dev server 

 

Thank you in advanced :) 

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