Add consequentialHint to ToolAnnotations

index.bs

@@ -187,6 +187,9 @@ An <dfn>annotations</dfn> is a [=struct=] with the following [=struct/items=]:
 
   : <dfn>untrusted content hint</dfn>
   :: a [=boolean=], initially false.
+
+  : <dfn>consequential hint</dfn>
+  :: a [=boolean=], initially false.
 </dl>
 
 
@@ -463,6 +466,9 @@ The <dfn method for=ModelContext>registerTool(<var>tool</var>, <var>options</var
       : [=annotations/untrusted content hint=]
       :: |tool|'s {{ModelContextTool/annotations}}'s {{ToolAnnotations/untrustedContentHint}}
 
+      : [=annotations/consequential hint=]
+      :: |tool|'s {{ModelContextTool/annotations}}'s {{ToolAnnotations/consequentialHint}}
+
    : [=tool definition/exposed origins=]
    :: |exposed origins|
 
@@ -574,9 +580,11 @@ The <dfn method for=ModelContext>getTools(<var>options</var>)</dfn> method steps
             : {{RegisteredTool/annotations}}
             :: if |tool definition|'s [=tool definition/annotations=] is not null, a
                {{ToolAnnotations}} dictionary whose {{ToolAnnotations/readOnlyHint}} is |tool
-               definition|'s [=tool definition/annotations=]'s [=annotations/read-only hint=] and
+               definition|'s [=tool definition/annotations=]'s [=annotations/read-only hint=],
                {{ToolAnnotations/untrustedContentHint}} is |tool definition|'s [=tool
-               definition/annotations=]'s [=annotations/untrusted content hint=].
+               definition/annotations=]'s [=annotations/untrusted content hint=], and
+               {{ToolAnnotations/consequentialHint}} is |tool definition|'s [=tool
+               definition/annotations=]'s [=annotations/consequential hint=].
 
          1. [=list/Append=] |registeredTool| to |tools|.
 
@@ -609,6 +617,7 @@ dictionary ModelContextTool {
 dictionary ToolAnnotations {
   boolean readOnlyHint = false;
   boolean untrustedContentHint = false;
+  boolean consequentialHint = false;
 };
 
 callback ToolExecuteCallback = Promise<any> (object input);
@@ -658,6 +667,9 @@ The {{ToolAnnotations}} dictionary provides optional metadata about a tool:
 
   : <code><var ignore>annotations</var>["{{ToolAnnotations/untrustedContentHint}}"]</code>
   :: If true, indicates that the tool's output contains data that is untrusted, from the perspective of the author registering the tool.
+
+  : <code><var ignore>annotations</var>["{{ToolAnnotations/consequentialHint}}"]</code>
+  :: If true, indicates that executing the tool will result in consequential actions that are significant, real-world, or non-reversible, ex: booking a flight, transferring money.
 </dl>
 
 
@@ -1299,6 +1311,14 @@ respective private browsing modes are safely exposed to [=agents=] and that thes
 
 **How:** A boolean {{ToolAnnotations/untrustedContentHint}} annotation that acts as a signal to the client that the payload requires heightened security handling, allowing the client to sanitize the payload, use indicators such as spotlighting [[SPOTLIGHTING]] to highlight untrustworthy content to the model, or hide that part of the response entirely.
 
+<h4 id="mitigation-consequential-annotation">Consequential Annotation for Tool Executions</h4>
+
+**What:** Providing agents with a signal that a tool's execution results in significant, real-world, or non-reversible consequences.
+
+**Threats addressed:** [[#misrepresentation-of-intent]]
+
+**How:** A boolean {{ToolAnnotations/consequentialHint}} annotation acts as a signal to the client or agent that the tool performs a consequential action, such as booking a flight or transferring money. This way they can selectively enforce mandatory user confirmation prompts before executing high-stakes tools, directly mitigating the risk of accidental or malicious misrepresentation of intent.
+
 <h2 id="accessibility">Accessibility considerations</h2>