Despite adopting a contract-first, standardized API best practice approach, Salvia Développement, a software publisher in the real estate sector, encountered difficulties in maintaining synchronous, point-to-point interoperability with its 1,200 customers. The increasing complexity, lack of reactivity and agility, hindered its ability to meet its customers’ evolving needs and to target new markets. In response, an asynchronous interoperability architectural style based on events was envisaged, leveraging an Event-Driven Architecture (EDA) implemented with webhooks. However, existing interoperability standards or software solutions such as OpenID Connect, JSON Web Token, MOM, ETL or OpenAPI, are not adapted for asynchronous interoperability needs in event description standardization and secure exchanges. This paper presents the initial findings from a collaborative effort with Nantes Université to address these issues. The first result is the establishment of interoperability between Salvia’s software, called SPO, and several CRM editors, by standardizing event and payload descriptions. The second result is the authentication and authorization of webhook callbacks by proposing a novel way of establishing authorization for callbacks without the need for a user account or even identification.