class ChatCompletionMessageGenericParam(BaseModel):
    role: Literal["system", "assistant", "tool"]
    content: Union[str, List[ChatCompletionMessageContentTextPart], None]
    tool_call_id: Optional[str] = None
    name: Optional[str] = None
    reasoning_content: Optional[str] = None
    tool_calls: Optional[List[ToolCall]] = Field(default=None, examples=[None])

    @field_validator("role", mode="before")
    @classmethod
    def _normalize_role(cls, v):
        if isinstance(v, str):
            v_lower = v.lower()
            if v_lower not in {"system", "assistant", "tool"}:
                raise ValueError(
                    "'role' must be one of 'system', 'assistant', or 'tool' (case-insensitive)."
                )
            return v_lower
        raise ValueError("'role' must be a string")