Worked on the HL7/fhir repository to enhance FHIR Messaging documentation, focusing on clarifying resource inclusion rules and the role of the MessageHeader. Improved guidance by explicitly stating that OperationDefinition and EventDefinition can define transmitted resources, and clarified that MessageHeader is not used for interpreting resources after removal from a Bundle. The approach involved removing redundant explanatory text and sharpening instructions for Bundle inclusions, directly linking changes to relevant FHIR JIRA issues for traceability. Utilized HTML and deep knowledge of FHIR standards to ensure the documentation is more accurate, maintainable, and accessible for developers working with interoperability requirements.