Please read this first

• Have you read the docs?Agents SDK docs yes
• Have you searched for related issues? Others may have faced similar issues. yes

Describe the bug

A clear and concise description of what the bug is.
What happened?
OpenAI Agents with LiteLLM does not properly provide the schema to Claude 4.1 Opus when attempting a tool call. This does not occur on LiteLLM version 1.74.2 and only in 1.75.0.

Debug information

• Agents SDK version: (e.g. v0.0.3)0.2.4
• Python version (e.g. Python 3.10) 3.11

Repro steps

Ideally provide a minimal python script that can be run to reproduce the bug.
What happened?

Construct a required schema like the following as the required arg for a @function_tool

class ActionType(StrEnum):
    FILL = "fill"
    PRESS = "press"
    CLICK = "click"
    SCROLL = "scroll"

class Instruction(BaseModel):
    action: ActionType
    instruction: str

Relevant log output

Model providing:

{
  "instruction": "Click the \"Portal Login\" button in the top right corner of the page"
}

omitting the ActionType entirely.

Expected behavior

A clear and concise description of what you expected to happen.
The expected behavior is it should be providing the ActionType as well.