Often agentic loops are especially applicable in diverse domains. In healthcare, a patient chart review requires querying multiple systems, cross-referencing drug interactions, and reasoning across clinical history. In legal work, a contract review needs case law search, clause comparison, and conflict detection — not to mention that you may want to bring in significant client context. The loop exists because these problems are hard to solve with workflow-based designs.
Independent of workflow vs. agentic approach, scenario-based evals are the right approach for domain-specific applications. Each scenario is a specific input — a patient chart, a contract, a claims record — paired with an expert-defined expected outcome. Did the agent identify the medication interaction? Did it flag the indemnification clause? Did it reach the correct coverage classification? Did it ask the right questions and not ask ones it already had access to through context?
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Why standard evals break for loops
Workflow-based implementations could test each step in isolation: given this input, does it produce the correct output to pass forward? In agentic loops, that no longer holds. The agent has autonomy over sequencing, and the order of operations may vary across sessions. Tool calls may fail or return unexpected results that the agent reasons past without flagging. An output-only eval catches none of it.
The non-determinism problem in domain evals
Here is where it gets genuinely hard. Evals are specific to a given scenario, but the agent’s path through that scenario is not fixed. Different sessions may pull different chunks from the retrieval system. The conversation may branch differently. The agent may reach the right conclusion through a different sequence of tool calls.
The way to handle this is to separate what you are actually testing. For the output layer, test the conclusion: did the agent identify the issue that matters? For the trajectory layer, test the key decision points: did it retrieve the document that contains the interaction? Did it call the drug lookup tool? Did it pass the correct patient ID? Trajectory evals do not require the agent to take an identical path every time. They require that the path passed through the checkpoints that justify the conclusion.
A case where the agent arrived at the right answer but skipped a critical tool call should not pass. That is not a correct evaluation. It is a lucky guess that will fail on the next prompt change.
How to start building this
You do not need a complete scenario library to get started.
- Start with production failures. Any trace where the agent reached a wrong conclusion, missed an issue, or called the wrong tool is a scenario waiting to be labeled. Get a domain expert to define correct behavior for that case and add it to the set. Five real failures are worth more than fifty synthetic happy-path cases.
- Write trajectory checkpoints, not just output assertions. For each scenario, identify the one or two tool calls or retrieval steps that are load-bearing. Test that those happened correctly and with the right parameters.
- Make “correct” explicit. Not a matching string, but a rubric: what must the output include, what must it not include, what tool calls must appear in the trace.
- Run evals on every significant change. Every prompt update, model upgrade, or tool integration should trigger a full scenario run. If scores drop, you do not ship.
The judge is itself a component to evaluate
Using LLM-as-judge to score outputs at scale is essential, but treat the judge as a component in your eval system, not a fixed oracle. Like every other component, it can drift. After a model update, your judge’s behavior may shift in ways you have not noticed. Build a calibration set for the judge: a sample of cases with human expert labels. Run the judge against them periodically and watch for divergence. When judge scores and expert scores disagree consistently, that is a signal. Either the judge has drifted, or your calibration set no longer reflects the scenarios the agent actually handles.
Treating the judge as infallible leads to calibration debt that accumulates invisibly and surfaces as production failures nobody predicted.
Reading list
- AI Agent Evaluations: A Developer’s Practical Guide (MLflow, 2025/2026) — Good on what specifically changes when you move from LLM to agent evals. The 75% judge-human agreement threshold as a recalibration trigger is a practical heuristic worth adopting. Apache-licensed tooling, no paywall.
- Evaluations for the Agentic World (QuantumBlack, January 2026) — Two detailed client case studies in regulated industries, a European telco and a European bank, covering trajectory validation, SME review as an eval layer, and continuous quality monitoring. The most concrete multi-agent eval case studies available in a public piece.
- A Pragmatic Guide to LLM Evals for Devs (Pragmatic Engineer, 2025) — The best starting point for teams new to systematic evals. Covers why LLM non-determinism breaks traditional testing and how to build a minimal eval suite that actually catches regressions. The golden dataset construction section is directly applicable to domain-specific scenario libraries.
- A Methodical Approach to Agent Evaluation (Google Cloud, November 2025) — The cleanest structural framework I have found: three pillars covering final output quality, trajectory analysis, and trust/safety. Worth reading specifically for the section on building a golden dataset when you do not yet have one. The Vertex AI mention at the end is a brief plug; the framework itself is tool-agnostic.
- Awesome-Evals (BenchFlow, GitHub) — A curated library of papers, blog posts, tools, and benchmarks organized by topic. Useful if you want to go deeper on any specific area: tool-calling evals, LLM-as-judge calibration, multi-agent evaluation. The “non-BS” framing in the description is accurate.









