fix: resolve context parameter detection for deferred annotations

src/google/adk/utils/context_utils.py

@@ -26,6 +26,7 @@
 from typing import Callable
 from typing import get_args
 from typing import get_origin
+from typing import get_type_hints
 from typing import Union
 
 # Re-export aclosing for backward compatibility
@@ -80,7 +81,12 @@ def find_context_parameter(func: Callable[..., Any]) -> str | None:
     signature = inspect.signature(func)
   except (ValueError, TypeError):
     return None
+  try:
+    hints = get_type_hints(func)
+  except (NameError, TypeError, AttributeError):
+    hints = {}
   for name, param in signature.parameters.items():
-    if _is_context_type(param.annotation):
+    annotation = hints.get(name, param.annotation)
+    if _is_context_type(annotation):
       return name
   return None

tests/unittests/tools/test_function_tool_with_import_annotations.py

@@ -16,8 +16,12 @@
 
 from typing import Any
 from typing import Dict
+from typing import Optional
 
 from google.adk.tools import _automatic_function_calling_util
+from google.adk.tools.function_tool import FunctionTool
+from google.adk.tools.tool_context import ToolContext
+from google.adk.utils.context_utils import find_context_parameter
 from google.adk.utils.variant_utils import GoogleLLMVariant
 from google.genai import types
 
@@ -177,3 +181,41 @@ def test_function() -> str:
   # VERTEX_AI should have response schema for string return (stored as string)
   assert declaration.response is not None
   assert declaration.response.type == types.Type.STRING
+
+
+def test_find_context_parameter_detects_custom_name_with_future_annotations():
+  """Test custom param name detection with deferred annotations."""
+
+  # pylint: disable-next=unused-argument
+  def my_tool(ctx: ToolContext) -> str:
+    """A tool with a custom-named context parameter."""
+    return ''
+
+  assert find_context_parameter(my_tool) == 'ctx'
+
+
+def test_find_context_parameter_optional_ctx_with_future_annotations():
+  """Test Optional[ToolContext] detection with deferred annotations."""
+
+  # pylint: disable-next=unused-argument
+  def my_tool(ctx: Optional[ToolContext] = None) -> str:
+    """A tool with an optional context parameter."""
+    return ''
+
+  assert find_context_parameter(my_tool) == 'ctx'
+
+
+def test_function_tool_excludes_custom_context_param_with_future_annotations():
+  """Test schema omits context param with deferred annotations."""
+
+  # pylint: disable-next=unused-argument
+  def my_tool(query: str, ctx: ToolContext) -> str:
+    """A tool with a custom-named context parameter."""
+    return query
+
+  tool = FunctionTool(my_tool)
+  declaration = tool._get_declaration()  # pylint: disable=protected-access
+
+  assert declaration.name == 'my_tool'
+  assert set(declaration.parameters.properties.keys()) == {'query'}
+  assert 'ctx' not in declaration.parameters.properties