Support agreements are usually negotiated in a comfortable moment and invoked in an uncomfortable one, which means the words matter far more than they seem to at signing. The most common defect is not a target that is too aggressive — it is a target that cannot be measured, or that measures something neither party actually cares about.
Start by separating response from resolution, because conflating them causes most disputes. Response time is when a human acknowledges and begins work, and it is entirely within your control. Resolution time is when the problem is fixed, and it depends on the nature of the fault, on third parties, and often on the client. Committing to resolution times for arbitrary faults is a promise you cannot keep; committing to response times, and to communication intervals during an incident, is one you can.
Severity definitions deserve real drafting effort, because that is where arguments actually happen. Define them by business impact rather than by technical symptom — production unavailable to all users, a core function unavailable, a function degraded with a workaround, a cosmetic issue — and state explicitly who classifies an incident and how disagreement is resolved. Without that, every serious incident begins with a debate about severity, which is exactly when nobody has time for it.
Be precise about coverage and the clock. Business hours in whose time zone. Which public holidays, given the client and the team may be in different countries with different calendars. Whether the clock pauses while awaiting information from the client, and how that pause is recorded. Whether an incident raised at ten minutes to close is a today problem or a tomorrow one. Each of these has caused real disputes, and each takes one sentence to prevent.
State the exclusions honestly and specifically. Faults in the client's infrastructure, third-party service outages, issues arising from changes the client made without notice, and anything outside the supported configuration. A support contract that appears to cover everything is one that will be invoked for everything, and the resulting relationship damage is worse than the awkward conversation at drafting time would have been.
Then measure it and report it monthly, unprompted, including the months you missed. Nothing builds confidence in a support relationship faster than a supplier who shows up with their own numbers before being asked, including the bad ones with an explanation. Nothing destroys it faster than a client discovering, during an escalation, that nobody has been measuring at all — because at that point every previous assurance becomes retrospectively doubtful.
