diff --git a/astrbot/core/tools/computer_tools/fs.py b/astrbot/core/tools/computer_tools/fs.py
index c3236c8a1..0b6003937 100644
--- a/astrbot/core/tools/computer_tools/fs.py
+++ b/astrbot/core/tools/computer_tools/fs.py
@@ -304,6 +304,11 @@ class FileReadTool(FunctionTool):
             )
             if not normalized_path:
                 raise ValueError("`path` must be a non-empty string.")
+            if local_env and os.path.isdir(normalized_path):
+                return (
+                    f"Error: '{normalized_path}' is a directory, not a file. "
+                    "Use a file path instead, or use 'astrbot_execute_shell' to list directory contents."
+                )
             offset, limit = self._validate_read_window(offset, limit)
             sb = await get_booter(
                 context.context.context,
diff --git a/tests/test_computer_fs_tools.py b/tests/test_computer_fs_tools.py
index 11571665a..17dbe3f6b 100644
--- a/tests/test_computer_fs_tools.py
+++ b/tests/test_computer_fs_tools.py
@@ -620,3 +620,23 @@ async def test_grep_tool_applies_result_limit(
     assert "match-2" in result
     assert "match-3" not in result
     assert "[Truncated to first 2 result groups.]" in result
+
+
+@pytest.mark.asyncio
+async def test_file_read_tool_rejects_directory_with_clear_message(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+):
+    """FileReadTool should return a helpful message when given a directory path."""
+    workspace = _setup_local_fs_tools(monkeypatch, tmp_path)
+    subdir = workspace / "my-directory"
+    subdir.mkdir()
+
+    result = await fs_tools.FileReadTool().call(
+        _make_context(),
+        path="my-directory",
+    )
+
+    assert "is a directory, not a file" in result
+    assert "my-directory" in result
+    assert "'astrbot_execute_shell'" in result