Many integrations fail because they are framed as technical projects. The real issue is usually data ownership, timing and edge cases no one mapped.
Before touching APIs, you need to decide which system is the source of truth for each entity, when synchronization happens and what should occur if the flow fails.
A useful integration includes observability, alerts and clear ownership. Otherwise teams only notice the issue when sales, finance or operations are already impacted.
Good integration reduces rework and improves visibility. It should not become another opaque layer.