You already have a review rubric. It probably says things like "the answer is clear, accurate and appropriately scoped." A human reviewer reads that and reaches for a judgment formed by years of context. An LLM judge reads the same sentence and has to guess what "clear" means at your company, on this product, for this audience.
The failure is structural, not a matter of model quality. Narration-style evaluation with arbitrary numeric scales is unstable: the same response can score a 7 in one run and a 9 in another, which is why practitioners recommend binary or a few clearly defined named categories instead of a 1 to 10 range the Evidently AI guide to LLM judges. If a human cannot apply your judging prompt consistently, the model will not either, and the usual fix is to rewrite the prompt until a person can.
The same lesson shows up in code review. Human-written code arrives with the author's intent, decision history and known constraints; agent-generated diffs arrive without them, so a reviewer has to reconstruct intent from the ticket and the target behavior before judging the patch the CodeRabbit review guide. Your judge is in exactly the reviewer's position: it sees the artifact, not the reasoning behind it. Give it checks that survive without the reasoning.
There is also a statistical reason to care. Rubric-based evaluation is now the standard approach for open-ended model output, but it depends on meticulous rubric design and continuous calibration against human experts, plus guardrails against known judge biases such as verbosity preference and self-preference a survey of rubric-based evaluation and LLM-as-judge methods. Calibration against humans is not optional polish. It is the measurement.
One decision rule to start with: write down what happens after the score before you write any criterion. A release gate, a model comparison and a regression monitor are three different measurement jobs and should not share a rubric just because they evaluate the same feature the QASkills rubric workflow. A release gate needs conservative detection of high-severity failures. A regression monitor needs labels that stay stable across runs. Write the decision contract in one sentence, then build criteria that serve only that sentence.



