refactor: avoid mutating config arg in registerAppTool

Author: ochafik

src/server/index.ts

@@ -48,7 +48,7 @@ export interface McpUiAppToolConfig extends ToolConfig {
         /**
          * URI of the UI resource to display for this tool.
          * This is converted to `_meta["ui/resourceUri"]`.
-         * 
+         *
          * @example "ui://weather/widget.html"
          *
          * @deprecated Use `_meta.ui.resourceUri` instead.
@@ -109,15 +109,16 @@ export function registerAppTool(
   const uiMeta = meta.ui as McpUiToolMeta | undefined;
   const legacyUri = meta[RESOURCE_URI_META_KEY] as string | undefined;
 
+  let normalizedMeta = meta;
   if (uiMeta?.resourceUri && !legacyUri) {
     // New format -> also set legacy key
-    meta[RESOURCE_URI_META_KEY] = uiMeta.resourceUri;
+    normalizedMeta = { ...meta, [RESOURCE_URI_META_KEY]: uiMeta.resourceUri };
   } else if (legacyUri && !uiMeta?.resourceUri) {
     // Legacy format -> also set new format
-    meta.ui = { ...uiMeta, resourceUri: legacyUri };
+    normalizedMeta = { ...meta, ui: { ...uiMeta, resourceUri: legacyUri } };
   }
 
-  server.registerTool(name, config, handler);
+  server.registerTool(name, { ...config, _meta: normalizedMeta }, handler);
 }
 
 /**