Identify the purchase decision
Can customers choose the right item without a specification discussion? List choices, availability and delivery information. If every order needs a site visit or quotation, a clear enquiry page may be the better first brief.
Plan the work behind checkout
Identify catalogue, stock, fulfilment and support owners. Agree payment requirements with the responsible team. Google provides guidance on sharing product information with search systems; operating the shop is a separate responsibility.
Review a sample order
Walk through selection, confirmation and handover, including a change or cancellation. Record what customers are told and who updates it. Use that exercise to decide launch scope rather than assuming every integration belongs in the first release.