The difficult part is often the availability rule.

Resources and constraints

One appointment with one staff member differs from a service needing two qualified people, a room and equipment. Preparation, cleanup and travel time can affect adjacent bookings.

Changes after booking

Include absence, rescheduling, cancellation, staff overrides and capacity changes. Define what customers may change themselves and what needs staff review.

Connected calendars and providers

List the calendar, CRM, payment and messaging tools. Choose an owning record and a visible response to failed or delayed updates. Provider features and access need review before a fixed scope.

Recurrence and waitlists

A series needs conflict rules for individual dates. A waitlist needs an offer lifetime and a decision about who receives the next opportunity. Include those cases rather than treating them as a single checkbox.

A useful first phase

Start with one service and location, checked resource availability and clear change rules. Add other services after the complete customer and staff path works.

Prepare a fictional booking, current tools, resource list, expected volume, access owner and deadline. Separate initial delivery from subscriptions and continuing support.