What is a required parameter in the InvocableMethod definition?

In the context of defining an InvocableMethod in Salesforce, the return type is a critical element because it specifies the type of data that the method will send back to the calling context, which can be another process, flow, or another Apex class. The InvocableMethod allows you to create Apex code that can be called from a Flow, making it crucial for automation scenarios where the process might need to return an outcome after performing its operations.

InvocableMethod is often used to expose Apex methods to Salesforce's Flow Builder, allowing non-developers to leverage the power of custom Apex methods in automated processes. Having a well-defined return type ensures that the Flow knows what to expect when the method is executed, which is essential for maintaining data integrity and for further processing the results downstream.

While parameters like Category, Description, and Label can enhance the usability and documentation of the method within the development environment, they are not enforceable requirements in the InvocableMethod definition. The return type, however, is essential for the functioning and compatibility of custom logic with the Flow framework, making it a required parameter.