Enhance function tool schemas with Annotated types (#1777)

Co-authored-by: Kazuhiro Sera <seratch@openai.com>

examples/basic/stream_function_call_args.py

@@ -1,5 +1,5 @@
 import asyncio
-from typing import Any
+from typing import Annotated, Any, Optional
 
 from openai.types.responses import ResponseFunctionCallArgumentsDeltaEvent
 
@@ -7,14 +7,18 @@ from agents import Agent, Runner, function_tool
 
 
 @function_tool
-def write_file(filename: str, content: str) -> str:
+def write_file(filename: Annotated[str, "Name of the file"], content: str) -> str:
     """Write content to a file."""
     return f"File {filename} written successfully"
 
 
 @function_tool
-def create_config(project_name: str, version: str, dependencies: list[str]) -> str:
-    """Create a configuration file for a project."""
+def create_config(
+    project_name: Annotated[str, "Project name"],
+    version: Annotated[str, "Project version"],
+    dependencies: Annotated[Optional[list[str]], "Dependencies (list of packages)"],
+) -> str:
+    """Generate a project configuration file."""
     return f"Config for {project_name} v{version} created"