diff --git a/nanobot/agent/tools/filesystem.py b/nanobot/agent/tools/filesystem.py
index a967073..da7778d 100644
--- a/nanobot/agent/tools/filesystem.py
+++ b/nanobot/agent/tools/filesystem.py
@@ -96,7 +96,7 @@ class ReadFileTool(_FsTool):
     async def execute(self, path: str | None = None, offset: int = 1, limit: int | None = None, **kwargs: Any) -> Any:
         try:
             if not path:
-                return f"Error: File not found: {path}"
+                return "Error reading file: Unknown path"
             fp = self._resolve(path)
             if not fp.exists():
                 return f"Error: File not found: {path}"
@@ -264,7 +264,7 @@ class EditFileTool(_FsTool):
             if old_text is None:
                 raise ValueError("Unknown old_text")
             if new_text is None:
-                raise ValueError("Unknown next_text")
+                raise ValueError("Unknown new_text")
 
             fp = self._resolve(path)
             if not fp.exists():
diff --git a/tests/test_filesystem_tools.py b/tests/test_filesystem_tools.py
index 76d0a51..ca6629e 100644
--- a/tests/test_filesystem_tools.py
+++ b/tests/test_filesystem_tools.py
@@ -77,6 +77,11 @@ class TestReadFileTool:
         assert "Error" in result
         assert "not found" in result
 
+    @pytest.mark.asyncio
+    async def test_missing_path_returns_clear_error(self, tool):
+        result = await tool.execute()
+        assert result == "Error reading file: Unknown path"
+
     @pytest.mark.asyncio
     async def test_char_budget_trims(self, tool, tmp_path):
         """When the selected slice exceeds _MAX_CHARS the output is trimmed."""
@@ -200,6 +205,13 @@ class TestEditFileTool:
         assert "Error" in result
         assert "not found" in result
 
+    @pytest.mark.asyncio
+    async def test_missing_new_text_returns_clear_error(self, tool, tmp_path):
+        f = tmp_path / "a.py"
+        f.write_text("hello", encoding="utf-8")
+        result = await tool.execute(path=str(f), old_text="hello")
+        assert result == "Error editing file: Unknown new_text"
+
 
 # ---------------------------------------------------------------------------
 # ListDirTool
@@ -265,6 +277,11 @@ class TestListDirTool:
         assert "Error" in result
         assert "not found" in result
 
+    @pytest.mark.asyncio
+    async def test_missing_path_returns_clear_error(self, tool):
+        result = await tool.execute()
+        assert result == "Error listing directory: Unknown path"
+
 
 # ---------------------------------------------------------------------------
 # Workspace restriction + extra_allowed_dirs