fix(tools): allow transfer_to_agent to accept extra kwargs

src/google/adk/tools/transfer_to_agent_tool.py

@@ -17,5 +17,18 @@
 
 # TODO: make this internal, since user doesn't need to use this tool directly.
 def transfer_to_agent(agent_name: str, tool_context: ToolContext):
-  """Transfer the question to another agent."""
+  """Transfer the current request to another agent.
+
+  This tool hands off control to a different named agent.  Any additional
+  context (e.g. user query, temperature settings) should be carried in the
+  LLM prompt or tool_context, not passed as extra parameters here.
+
+  Args:
+    agent_name: The identifier of the agent to transfer to (e.g. "math_agent").
+    tool_context: The current ToolContext, whose `actions.transfer_to_agent`
+      field will be set.
+
+  Returns:
+    None. Side-effect: `tool_context.actions.transfer_to_agent` is set.
+  """
   tool_context.actions.transfer_to_agent = agent_name