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Add ToolActivatedEvent and ToolCancelEvent interfaces #146

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Add ToolActivatedEvent and ToolCancelEvent interfaces
beaufortfrancois Mar 19, 2026
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Merge branch 'main' of github.com:webmachinelearning/webmcp into events
beaufortfrancois May 27, 2026
9f30276
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beaufortfrancois May 27, 2026
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58 changes: 58 additions & 0 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,8 @@ interface ModelContext : EventTarget {
undefined registerTool(ModelContextTool tool, optional ModelContextRegisterToolOptions options = {});

attribute EventHandler ontoolchange;
attribute EventHandler ontoolactivated;
attribute EventHandler ontoolcancel;
};
</xmp>

Expand Down Expand Up @@ -589,6 +591,56 @@ The <dfn method for=ModelContextClient>requestUserInteraction(<var ignore>callba

</div>

<h4 id="tool-activated-event">ToolActivatedEvent Interface</h4>

The {{ToolActivatedEvent}} interface represents a {{ModelContext/toolactivated}} event that is dispatched at {{ModelContext}} when a tool is invoked by an [=agent=].

<xmp class="idl">
[Exposed=Window, SecureContext]
interface ToolActivatedEvent : Event {
constructor(DOMString type, optional ToolActivatedEventInit eventInitDict = {});
readonly attribute DOMString toolName;
readonly attribute Element? element;
};

dictionary ToolActivatedEventInit : EventInit {
DOMString toolName = "";
Element? element = null;
};
</xmp>

<dl class="domintro" dfn-type=attribute dfn-for=ToolActivatedEvent>
: <dfn>toolName</dfn>
:: Returns the name of the tool that was activated.
: <dfn>element</dfn>
:: Returns the form element associated with the tool, if any.
</dl>

<h4 id="tool-cancel-event">ToolCancelEvent Interface</h4>

The {{ToolCancelEvent}} interface represents a {{ModelContext/toolcancel}} event that is dispatched at {{ModelContext}} when a tool's invocation is canceled by an [=agent=].

<xmp class="idl">
[Exposed=Window, SecureContext]
interface ToolCancelEvent : Event {
constructor(DOMString type, optional ToolCancelEventInit eventInitDict = {});
readonly attribute DOMString toolName;
readonly attribute Element? element;
};

dictionary ToolCancelEventInit : EventInit {
DOMString toolName = "";
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@bwalderman bwalderman Mar 19, 2026

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Looking at this interface, I'm seeing a potential problem with multiple agents and concurrent activations of the same tool. Which one should be cancelled if all we know is the tool name? I'll comment on the issue.

Element? element = null;
};
</xmp>

<dl class="domintro" dfn-type=attribute dfn-for=ToolCancelEvent>
: <dfn>toolName</dfn>
:: Returns the name of the tool that was canceled.
: <dfn>element</dfn>
:: Returns the form element associated with the tool, if any.
</dl>

<h3 id="declarative-api">Declarative WebMCP</h3>

This section is entirely a TODO. For now, refer to the [explainer draft](https://github.com/webmachinelearning/webmcp/pull/76).
Expand Down Expand Up @@ -631,6 +683,12 @@ that must be supported, as [=event handler IDL attributes=], by all {{ModelConte
<tr>
<td><dfn attribute for="ModelContext">ontoolchange</dfn>
<td><dfn event for="ModelContext">toolchange</dfn>
<tr>
<td><dfn attribute for="ModelContext">ontoolactivated</dfn>
<td><dfn event for="ModelContext">toolactivated</dfn>
<tr>
<td><dfn attribute for="ModelContext">ontoolcancel</dfn>
<td><dfn event for="ModelContext">toolcancel</dfn>
</table>

<h3 id="permissions-policy">Permissions policy integration</h3>
Expand Down
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