int | None union syntax fails to parse in function parameters despite documented support

Bug Description:

The Google ADK function parameter parser fails to handle modern Python union syntax (int | None) in function parameters, throwing a parsing error despite the codebase claiming to support union types. The error suggests using manual function declaration parsing as a workaround.

To Reproduce:

Create a function with int | None parameter annotation
Use the function as a tool in an ADK agent
Run the agent - automatic function calling fails with parsing error
Expected Behavior:
The int | None syntax should be parsed successfully, similar to how Optional[int] works, since both represent the same type annotation.

Actual Behavior:

Error: Failed to parse the parameter num_lines: int | None of function for automatic function calling. Automatic function calling works best with simpler function signature schema, consider manually parsing your function declaration for function .

Root Cause Analysis:
The issue appears to be in where the parser checks get_origin(param.annotation) is Union. The modern int | None syntax may not be detected by this condition, causing it to fall through to the error case at .

Environment:

Python version: 3.12.10
ADK version: 1.4.2
OS: Windows 11 Pro
Code Example:

```python
def example_function(file_path: str, num_lines: int | None = None) -> str:
# Function implementation
pass
```
Workaround:
Using Optional[int] instead of int | None works as expected:

from typing import Optional
```python
def example_function(file_path: str, num_lines: Optional[int] = None) -> str:
# Function implementation
pass
```
Additional Context:

The codebase requires from __future__ import annotations as shown in check-file-contents.yml:73-83
The parser has logic for handling union types with None as shown in
The codebase uses Optional[type] extensively in existing tools, suggesting this should work
This appears to be an inconsistency between the documented/intended support for modern Python syntax and the actual implementation in the parameter parser.