PackCheck: Every Count Accounted For

PackCheck helps a person checking a small order keep an inspectable record of declared quantities. Saying a count is only the beginning: AssemblyAI's Voice Agent API calls a deterministic checklist engine that validates item IDs, quantity limits and revisions before changing anything. The working prototype supports corrections, undo, explicit review, finalization and JSON receipt export. Repeated tool-call IDs cannot duplicate a change. Rejected attempts do not replace the last accepted action. A receipt verifier reproduces the final state without an AI model. The browser includes manual rehearsal and a clearly labelled replay of actual API evidence, so evaluators can inspect the workflow without spending API credit. Our synthetic integration used one real AssemblyAI session and eight tool calls: blue mugs changed from zero to two, back to one and finally two; one red mug completed the counts. A programmatic review finalized a receipt that passes replay. The session sent its termination message but closed with WebSocket code 1006 without server acknowledgement; this unresolved teardown limitation remains visible in the evidence. PackCheck is an open, focused prototype, not proof of physical box contents. It has no warehouse trial, user study or measured productivity claim. Microphone capture is implemented but not field-tested. Codex assisted development; synthetic input audio provenance is documented. The contribution is the complete, auditable workflow, not a claim to have invented voice picking.