diff --git a/packages/core/src/tools/send-message.ts b/packages/core/src/tools/send-message.ts
index 6c863783f3c..49cb6eb6570 100644
--- a/packages/core/src/tools/send-message.ts
+++ b/packages/core/src/tools/send-message.ts
@@ -336,12 +336,6 @@ export class SendMessageTool extends BaseDeclarativeTool<
           },
         },
         required: ['message'],
-        // Either a teammate recipient (`to`) or a background-task
-        // (`task_id`) must be specified — they correspond to the
-        // two routing modes. Letting the model send `{message}`
-        // alone wastes a round-trip on the runtime "Recipient is
-        // required" error.
-        oneOf: [{ required: ['to'] }, { required: ['task_id'] }],
         additionalProperties: false,
       },
       true, // isOutputMarkdown