Method for lower error chance in output parser

OSS Product Help
1 
    ans_chat_prompt = ChatPromptTemplate.from_messages([
        SystemMessagePromptTemplate.from_template(ans_grading_system_template),
        HumanMessagePromptTemplate.from_template(ans_grading_human_template)
    ])
    ans_chat_prompt = ans_chat_prompt.partial(format_instructions=parser.get_format_instructions())
    ans_chat = ans_chat_prompt.format_messages(
        question=query,
        answer=answer,
        research_source=research_agent,
        context=format_docs(contexts),
        keywords=", ".join(keywords),
        time=time,
        branch_name=branch_name,
        bot_name=bot_name,
        format_instructions=parser.get_format_instructions()
    )        
    grading_response = llm.invoke(ans_chat)
   
    grading_response = grading_response.content.strip()
    parsed_resp = parser.parse(grading_response)
    grading_result = self._parse_grading_response(parsed_resp)

Is there any method to ensure there is 100% chance of error free for output parser? Currenly i use I am using vertexAI and trying to have a structured output in a single LLM call. I also wonder does Gemini support ProductStrategy?