refactor(session): tighten cross-session access

tests/tools/test_tool_registry.py

@@ -9,9 +9,16 @@ from nanobot.agent.tools.registry import ToolRegistry
 
 
 class _FakeTool(Tool):
-    def __init__(self, name: str, schema: dict[str, Any] | None = None):
+    def __init__(
+        self,
+        name: str,
+        schema: dict[str, Any] | None = None,
+        *,
+        available: bool = True,
+    ):
         self._name = name
         self._schema = schema
+        self._available = available
 
     @property
     def name(self) -> str:
@@ -28,6 +35,9 @@ class _FakeTool(Tool):
     async def execute(self, **kwargs: Any) -> Any:
         return kwargs
 
+    def available(self) -> bool:
+        return self._available
+
 
 def _tool_names(definitions: list[dict[str, Any]]) -> list[str]:
     names: list[str] = []
@@ -59,6 +69,19 @@ def test_get_definitions_orders_builtins_then_mcp_tools() -> None:
     ]
 
 
+def test_unavailable_tools_are_hidden_and_cannot_be_called() -> None:
+    registry = ToolRegistry()
+    registry.register(_FakeTool("visible"))
+    registry.register(_FakeTool("hidden", available=False))
+
+    assert _tool_names(registry.get_definitions()) == ["visible"]
+    tool, params, error = registry.prepare_call("hidden", {})
+
+    assert tool is None
+    assert params == {}
+    assert error == "Error: Tool 'hidden' is unavailable"
+
+
 def test_prepare_call_rejects_near_miss_tool_name_with_suggestion() -> None:
     registry = ToolRegistry()
     registry.register(_FakeTool("read_file"))