The team can't find existing standards. Help them build a rubric.
Ask: what does the output look like when it's right? Get specific, measurable answers. File sizes, response times, value ranges, visual correctness, behavioral expectations. If the user or team can't quantify it, ask what they'd check manually. If they don't know the values yet, the rubric item becomes an experiment: produce a sample, measure the property, decide if it's acceptable.
The rubric is a short list of pass/fail criteria the team agrees on before execution starts. Keep it concrete.
The team will review output against these criteria in a loop — refining until confidence reaches 9/10+. Write criteria that guide improvement, not just pass/fail. When no test suite exists, this rubric is the testing framework.