Describe the utility of a tool's origin

Author: domfarolino

index.bs

@@ -725,13 +725,13 @@ dictionary RegisteredTool {
      [[!JSON-SCHEMA]].
 
   : <code><var ignore>tool</var>["{{RegisteredTool/title}}"]</code>
-  :: A human-readable label for the tool.
+  :: A human-readable label for the tool. It is the same value provided at tool registration, via {{ModelContextTool/title}}.
 
   : <code><var ignore>tool</var>["{{RegisteredTool/window}}"]</code>
   :: The {{Window}} of the document that registered the tool.
 
   : <code><var ignore>tool</var>["{{RegisteredTool/origin}}"]</code>
-  :: The origin of the document that registered the tool.
+  :: The origin of the document that registered the tool. This member is only meaningful when the tool is cross-origin, and the consumer of a tool cannot otherwise get the tool's origin from its {{RegisteredTool/window}}. For same-origin tools, this is the same as the tool's {{RegisteredTool/window}}'s {{WindowOrWorkerGlobalScope/origin}}, and the caller's own {{Window}}.{{WindowOrWorkerGlobalScope/origin}}.
 
   : <code><var ignore>tool</var>["{{RegisteredTool/annotations}}"]</code>
   :: Optional annotations providing metadata about the tool.