· 11 min read
OpenAPI Cannot Describe Your Events: Seven Things an Event Contract Must State
Request-response interface description formats cannot express an event-driven contract. There is no caller, there is no meaningful response, delivery is at-least-once, and ordering is not guaranteed. Teams document their events in a request-response format anyway, and the resulting document omits exactly the properties that cause incidents. Here are the seven things an event contract has to state, and how a unique index becomes the place the contract is actually enforced.