diff --git a/src/main/java/com/claudecode/tool/impl/TodoWriteTool.java b/src/main/java/com/claudecode/tool/impl/TodoWriteTool.java
index 750c4d3..886083c 100644
--- a/src/main/java/com/claudecode/tool/impl/TodoWriteTool.java
+++ b/src/main/java/com/claudecode/tool/impl/TodoWriteTool.java
@@ -25,6 +25,11 @@ public class TodoWriteTool implements Tool {
         return "TodoWrite";
     }
 
+    @Override
+    public boolean isReadOnly() {
+        return true; // 仅操作内存中的 todo 列表，无文件系统副作用
+    }
+
     @Override
     public String description() {
         return """