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Spec unregisterTool(ModelContextTool) #147

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17fcafc
Spec `unregisterTool(ModelContextTool)`
domfarolino Mar 19, 2026
2859d03
Remove during
domfarolino Mar 20, 2026
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55 changes: 49 additions & 6 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,14 @@ A <dfn>tool definition</dfn> is a [=struct=] with the following [=struct/items=]
: <dfn>description</dfn>
:: a [=string=].

: <dfn>imperative input schema object</dfn>
:: an {{object}}-or-null, initially null.

Note: This is only populated for tools registered by the imperative form of this API (i.e.,
{{ModelContext/registerTool()}}. In that case, it holds the raw
{{ModelContextTool/inputSchema}} object, and is used in
{{ModelContext/unregisterTool()}} to find the right tool to unregister.

: <dfn>input schema</dfn>
:: a [=string=].

Expand Down Expand Up @@ -178,7 +186,7 @@ The {{ModelContext}} interface provides methods for web applications to register
[Exposed=Window, SecureContext]
interface ModelContext {
undefined registerTool(ModelContextTool tool);
undefined unregisterTool(DOMString name);
undefined unregisterTool(ModelContextTool tool);
};
</xmp>

Expand All @@ -189,12 +197,15 @@ is a [=model context=] [=struct=] created alongside the {{ModelContext}}.
<dl class="domintro">
<dt><code><var ignore>navigator</var>.{{Navigator/modelContext}}.{{ModelContext/registerTool(tool)}}</code></dt>
<dd>
<p>Registers a single tool without clearing the existing set of tools. The method throws an error, if a tool with the same name already exists, or if the {{ModelContextTool/inputSchema}} is invalid.
<p>Registers a single tool without clearing the existing set of tools. This method throws an
exception if a tool with the same name already exists, or if the
{{ModelContextTool/inputSchema}} is invalid.</p>
</dd>

<dt><code><var ignore>navigator</var>.{{Navigator/modelContext}}.{{ModelContext/unregisterTool(name)}}</code></dt>
<dt><code><var ignore>navigator</var>.{{Navigator/modelContext}}.{{ModelContext/unregisterTool(tool)}}</code></dt>
<dd>
<p>Removes the tool with the specified name from the registered set.
<p>Removes the tool from the registered set of tools. This method throws an exception if no
matching tool has been registered.</p>
</dd>
</dl>

Expand Down Expand Up @@ -257,13 +268,45 @@ The <dfn method for=ModelContext>registerTool(<var>tool</var>)</dfn> method step
</div>

<div algorithm>
The <dfn method for=ModelContext>unregisterTool(<var>name</var>)</dfn> method steps are:
The <dfn method for=ModelContext>unregisterTool(<var>tool</var>)</dfn> method steps are:

1. Let |tool map| be [=this=]'s [=ModelContext/internal context=]'s [=model context/tool map=].

1. If |tool map|[|name|] does not [=map/exist=], then [=exception/throw=] an {{InvalidStateError}}
1. Let |name| be |tool|'s {{ModelContextTool/name}}.

1. If |tool map|[|name|] does not [=map/exist=], then [=exception/throw=] an {{NotFoundError}}
{{DOMException}}.

1. Let |registered tool| be |tool map|[|name|].

1. Let |matches| be true.

1. [=Assert=]: |name| equals |registered tool|'s [=tool definition/name=].

1. If |tool|'s {{ModelContextTool/description}} does not equal |registered tool|'s [=tool
definition/description=], then set |matches| to false.

1. Else if |tool|'s {{ModelContextTool/inputSchema}} [=map/exists=] and |registered tool|'s [=tool
definition/imperative input schema object=] is null, or if |tool|'s
{{ModelContextTool/inputSchema}} does not [=map/exist=] but |registered tool|'s [=tool
definition/imperative input schema object=] is not null, then set |matches| to false.

1. Else if |tool|'s {{ModelContextTool/inputSchema}} [=map/exists=] and is not the same object as
|registered tool|'s [=tool definition/imperative input schema object=], then set |matches| to
false.

1. Else if |tool|'s {{ModelContextTool/execute}} is not the same [=callback function=] that
|registered tool|'s [=tool definition/execute steps=] is prepared to run, then set |matches| to
false.

1. Let |tool read-only hint| be true if |tool|'s {{ModelContextTool/annotations}} [=map/exists=] and
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@bwalderman bwalderman Mar 19, 2026

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Can we split out the annotation matching into a separate algorithm that this references? That should hopefully avoid issues where we add new annotations but forget to include them in the steps here.

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@domfarolino domfarolino Mar 20, 2026

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Hmm, do you think it's less likely we'll forget to add checks there than here? I'm wondering if we should just factor out a more general matching algorithm for the whole tool, so everything can go in one place, instead of being spread across two places. How do you feel about that?

its {{ToolAnnotations/readOnlyHint}} is true; false otherwise.

1. If |tool read-only hint| does not equal |registered tool|'s [=tool definition/read-only hint=],
then set |matches| to false.

1. If |matches| is false, then [=exception/throw=] an {{NotFoundError}} {{DOMException}} and return.

1. [=map/Remove=] |tool map|[|name|].

</div>
Expand Down