Agree what success means.
Start with an objective that the work can influence and a definition that both teams understand. For a website, that may involve a clearer enquiry journey and a verifiable form handoff. For a campaign, it may involve agreed conversion definitions and a review of lead quality. We distinguish delivery commitments from commercial outcomes that depend on the market, the offer and the client's sales process. A written scope records the deliverables, assumptions, exclusions and the basis for acceptance.