 Interoperability is crucial for research infrastructures that offer services and scholarly works content that need to be exchanged, processed, and analyzed among different information, communication, and technology systems. Open-air interoperability guidelines documents and collects the standards, rules, and processes that any interested party needs to follow to connect with open-air infrastructure and, therefore, EOSC. How many levels of interoperability should a system comply with to connect with open-air? Legal, operational, semantic, and technical. Open-air interoperability guidelines offers information on literature, institutional, and somatic repositories, data archives, current research information systems, software, and other research products. To run a compatibility test with Open-air, you can use the Open-air Metadata Validator service within Open-air Provide. The guidelines can help you to make your service, content, infrastructure compliant with Open-air and EOSC. Minimize the risk of legal, technical, and operational failures. Get broader visibility and demonstrate impact on a local, national, and international level. Follow the standards of the Open Science Ecosystem for seamless operations. Enrich your metadata. Reach interconnected systems that speak the same language with your system and produce comprehensive, fair, and innovative outcomes. It's a service for content and service providers. Research infrastructures. The guidelines are available openly online and updated when new information becomes available. Research community members can participate in discussions and contribute further improvements. Open-air interoperability in practice.