diff --git a/astrbot/core/computer/file_read_utils.py b/astrbot/core/computer/file_read_utils.py
index 5b5fd9fc8e..3e0432bcf5 100644
--- a/astrbot/core/computer/file_read_utils.py
+++ b/astrbot/core/computer/file_read_utils.py
@@ -652,6 +652,12 @@ async def read_file_tool_result(
     workspace_dir: str | None = None,
 ) -> ToolExecResult:
     if local_mode:
+        if Path(path).is_dir():
+            return (
+                f"Error: `{path}` is a directory, not a file. "
+                "Provide a file path instead, or use `astrbot_execute_shell` "
+                "to list directory contents."
+            )
         probe_payload = await _probe_local_file(path)
     else:
         probe_payload = await _exec_python_json(
diff --git a/tests/test_computer_fs_tools.py b/tests/test_computer_fs_tools.py
index 11571665a5..61586aee93 100644
--- a/tests/test_computer_fs_tools.py
+++ b/tests/test_computer_fs_tools.py
@@ -450,6 +450,25 @@ async def test_file_read_tool_allows_partial_read_for_large_text_file(
     assert result == "".join(lines[1000:1003])
 
 
+@pytest.mark.asyncio
+async def test_file_read_tool_reports_directory_clearly(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+):
+    workspace = _setup_local_fs_tools(monkeypatch, tmp_path)
+    (workspace / "some_dir").mkdir()
+
+    result = await fs_tools.FileReadTool().call(
+        _make_context(),
+        path="some_dir",
+    )
+
+    assert isinstance(result, str)
+    assert "is a directory" in result
+    assert "astrbot_execute_shell" in result
+    assert "Permission denied" not in result
+
+
 @pytest.mark.asyncio
 async def test_file_read_tool_returns_image_call_tool_result_for_images(
     monkeypatch: pytest.MonkeyPatch,