Artificial intelligence (AI) has rapidly expanded the scale and ambition of materials research, enabling property prediction, candidate screening, and data-driven optimization across large chemical and structural spaces. However, the field still lacks a discipline-specific standard for scientific accountability: a structured way to report what an AI output legitimately warrants, under which assumptions, and with what limitations. This gap is not cosmetic; it is epistemic. Materials AI often converts heterogeneous proxies (composition features, crystal graphs, microstructure descriptors) into numerical predictions. Yet, manuscripts frequently present these outputs as claims of generality, mechanism, or design readiness without specifying the scope conditions that would make such claims defensible. Recent progress in graph neural networks, benchmark suites, and large community datasets improves comparability. Still, it also amplifies risks of leakage, distribution shift, and proxy instability, which can inflate conclusions while remaining underreported. Meanwhile, uncertainty quantification and explainable AI are increasingly used as trust signals, even though both can be misunderstood when their semantics are not clearly stated, and their limitations are not operationalized for decision-making. We propose a novel conceptual standard—the Scientific Accountability Sheet (SAS)—which binds reported claims to explicit claim types, scope boundaries, evidence anchors, uncertainty semantics, and decision admissibility. SAS reframes “responsible reporting” as a scientific warrant structure rather than an optional best-practice appendix.