diff --git a/src/agents/mcp/util.py b/src/agents/mcp/util.py
index bf00cb2b79..a487567c52 100644
--- a/src/agents/mcp/util.py
+++ b/src/agents/mcp/util.py
@@ -665,7 +665,7 @@ async def invoke_mcp_tool(
 
         # If structured content is requested and available, use it exclusively
         tool_output: ToolOutput
-        if server.use_structured_content and result.structuredContent:
+        if server.use_structured_content and result.structuredContent is not None:
             tool_output = json.dumps(result.structuredContent)
         else:
             tool_output_list: list[ToolOutputItem] = []