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A correct final payment total does not prove an agent followed the payment contract. In this synthetic teaching case, one run passes, one violates the contract despite ending at the same $50 net total, and one cannot be scored because its trace omits key evidence. Reliable grading checks each contract condition—and whether the trace can establish it—rather than looking only at the final balance.
The contract is more than a final total
The example describes a synthetic task, not a real payment incident. Its contract is to refund order A exactly $50, once, after an authorization valid for that order and amount, without changing unrelated orders. The order starts with no refund. A retry is allowed when it uses the same idempotency key, returns the original receipt, and creates no second effect.
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That wording defines what counts as success. A final net total can show the financial result, but it cannot by itself establish the order of events, which order was targeted, how many effects occurred, or whether unrelated state changed.
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| Trace | What the evidence shows | Verdict |
|---|---|---|
| A | Authorization for order A and $50 precedes one refund effect. A retry with the same key returns the same receipt and creates no additional effect. | Pass, assuming the trace is trustworthy and the stated initial state is correct. |
| B | One effect occurs before authorization. A second effect is then issued under another key and reversed. The net payment is still $50. | Violation. The reversal does not erase the earlier out-of-order effect or make the second issued effect disappear. |
| C | The trace shows a net $50 payment but provides no authorization or intermediate events. | Unscorable. The evidence establishes neither compliance nor a violation. |
Trace B exposes the weakness in a total-only grader: “The net total is correct and the run is still a violation,” as the DEV Community account redsoft puts it. Trace C needs a distinct outcome too: “We cannot tell from this evidence” is not a pass or a failure. Both quotations describe the synthetic example, not production behavior.
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Grade the contract condition by condition
For this contract, evaluate these checks independently:
- Authorization and order: Was there a valid authorization for order A and $50 before the refund effect?
- Target and amount: Did the effect apply to the intended order for exactly $50?
- Effect count: Did exactly one successful refund effect occur?
- Retry behavior: If retried, did the same idempotency key return the original receipt without causing another effect?
- Isolation: Did unrelated order state remain unchanged?
- Evidence sufficiency: Is the trace complete enough to establish the first five checks?
Do not average these into a single score. A passing total or a high aggregate score can conceal one failed condition, while missing evidence can be mistaken for success. Keep the verdict tied to the contract: a different contract that explicitly permits reversals may call for different checks and a different interpretation.
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Unknown payment status is a decision point, not a retry signal
If a provider returns a status that is neither success nor failure, the trace does not yet establish whether an effect occurred. Before retrying, the evidence needs to resolve that uncertainty—such as whether the original request took effect and whether a retry would be recognized as the same operation. In this case, the specified safe retry is one with the same idempotency key that returns the original receipt without a new effect. A grader should mark an unresolved trace unscorable rather than infer success or failure from the final total alone.
Test whether the trace can be trusted
These checks depend on observing the relevant events. They do not prove that a logger records every effect: a missing event could make a violating run look compliant. Test logging separately by injecting a known duplicate effect and confirming that it appears in the log. Even then, this teaching case establishes no coverage of other task contracts, no acceptable risk threshold, and no transferable grading cutoff.
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The practical question for an agent test is not only whether the balance ends up right. If it would pass Trace B, ask: “what else are they passing?”
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