How would you design and calibrate an LLM-as-a-judge evaluator?

Builds a focused scoring guide, representative labeled examples, bias checks, and ongoing agreement monitoring for model-based evaluation.

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TL;DR

I give the judge one focused question, explicit criteria, the relevant input and evidence, and a constrained score such as pass or fail with a reason. I compare its decisions against expert-labeled examples before using it at scale. Calibration checks overall agreement and the kinds of cases where the judge disagrees, because a good average can still hide a systematic bias.

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Practice focus

Rubric design, judge validation, bias control, reproducibility, and operational calibration.

Answer first

Answer path

Core answer first, then checkpoints toward a stronger answer.

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Core answer
Start here. This is the direct spoken answer to practice first.
Overview
A judge model is another probabilistic component and needs its own evaluation.
I give the judge one focused question, explicit criteria, the relevant input and evidence, and a constrained score such as pass or fail with a reason. I compare its decisions against expert-labeled examples before using it at scale. Calibration checks overall agreement and the kinds of cases where the judge disagrees, because a good average can still hide a systematic bias.
Checkpoint
Stronger answer
Optional upgrade with examples, trade-offs, and sharper phrasing.
The calibration set includes clear passes, clear failures, borderline cases, different response lengths, and difficult slices. For pairwise judging I randomize or reverse answer order to detect position bias, and I check whether verbosity is being mistaken for quality. Examples anchor each scoring guide level, while references are supplied only when the task genuinely has a defensible reference answer.

Review signals

Use these to catch weak phrasing, shallow reasoning, and risky claims.

Common mistakesCandidateCommon mistakesMistakes that weaken the answer or signal shallow understanding.Open details

Details

Asking a judge whether an answer is generally good.
Calibrating only on obvious examples.
Changing the judge and comparing scores without a bridge study.

How would you design and calibrate an LLM-as-a-judge evaluator?

Practice focus

Answer path

Overview

Review signals

Follow-up prompts

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