| Accuracy | Correctness on a held-out set of the system's real tasks, scored against reference outputs or rubrics. | The headline dimension, but only meaningful on this system's inputs, not on a public benchmark. |
| Task reliability | How often the model completes the whole task as specified, across repeated runs and input variants. | A model that is right most of the time and wrong unpredictably is a bug, not a feature. |
| Structured-output quality | Schema adherence, field completeness and type correctness of typed outputs, before any repair step. | Downstream code consumes the output. Every repair step is latency, cost and a hidden failure mode. |
| Latency | Time to first token and to completion at the prompt sizes the system actually sends, median and tail. | Decides whether a step can be synchronous and how many steps a workflow can afford. |
| Cost | Cost per completed task at production volumes, including retries and validation reruns. | Per-call price is misleading. Per-successful-task cost is what the budget sees. |
| Context handling | Quality at the context lengths the system needs, including retrieval-heavy prompts and long documents. | Many models degrade quietly as context grows. The degradation has to be measured, not assumed. |
| Failure patterns | What goes wrong: invented fields, refusals, truncation, format drift, and how detectable each failure is. | Detectable failures can be caught by validation. Silent ones reach users. |
| Consistency | Variance across repeated runs of the same input and across paraphrased inputs. | Users and downstream systems need the same answer to the same question. |