diff --git a/nanobot/agent/tools/filesystem.py b/nanobot/agent/tools/filesystem.py
index 4f83642..da7778d 100644
--- a/nanobot/agent/tools/filesystem.py
+++ b/nanobot/agent/tools/filesystem.py
@@ -93,8 +93,10 @@ class ReadFileTool(_FsTool):
             "required": ["path"],
         }
 
-    async def execute(self, path: str, offset: int = 1, limit: int | None = None, **kwargs: Any) -> Any:
+    async def execute(self, path: str | None = None, offset: int = 1, limit: int | None = None, **kwargs: Any) -> Any:
         try:
+            if not path:
+                return "Error reading file: Unknown path"
             fp = self._resolve(path)
             if not fp.exists():
                 return f"Error: File not found: {path}"
@@ -174,8 +176,12 @@ class WriteFileTool(_FsTool):
             "required": ["path", "content"],
         }
 
-    async def execute(self, path: str, content: str, **kwargs: Any) -> str:
+    async def execute(self, path: str | None = None, content: str | None = None, **kwargs: Any) -> str:
         try:
+            if not path:
+                raise ValueError("Unknown path")
+            if content is None:
+                raise ValueError("Unknown content")
             fp = self._resolve(path)
             fp.parent.mkdir(parents=True, exist_ok=True)
             fp.write_text(content, encoding="utf-8")
@@ -248,10 +254,18 @@ class EditFileTool(_FsTool):
         }
 
     async def execute(
-        self, path: str, old_text: str, new_text: str,
+        self, path: str | None = None, old_text: str | None = None,
+        new_text: str | None = None,
         replace_all: bool = False, **kwargs: Any,
     ) -> str:
         try:
+            if not path:
+                raise ValueError("Unknown path")
+            if old_text is None:
+                raise ValueError("Unknown old_text")
+            if new_text is None:
+                raise ValueError("Unknown new_text")
+
             fp = self._resolve(path)
             if not fp.exists():
                 return f"Error: File not found: {path}"
@@ -350,10 +364,12 @@ class ListDirTool(_FsTool):
         }
 
     async def execute(
-        self, path: str, recursive: bool = False,
+        self, path: str | None = None, recursive: bool = False,
         max_entries: int | None = None, **kwargs: Any,
     ) -> str:
         try:
+            if path is None:
+                raise ValueError("Unknown path")
             dp = self._resolve(path)
             if not dp.exists():
                 return f"Error: Directory not found: {path}"
diff --git a/pyproject.toml b/pyproject.toml
index bbae925..7cc0094 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -70,6 +70,7 @@ dev = [
     "matrix-nio[e2e]>=0.25.2",
     "mistune>=3.0.0,<4.0.0",
     "nh3>=0.2.17,<1.0.0",
+    "mypy>=1.19.1",
 ]
 
 [project.scripts]
diff --git a/tests/test_filesystem_tools.py b/tests/test_filesystem_tools.py
index cab2c94..f3069a7 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
@@ -263,6 +275,11 @@ 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