An integration procedure contains a Remote Action element that calls a method of an APEXclass. The method requires two fields are input: Accountid…

The Remote Action element must be configured to construct a new JSON object that matches the Apex method's required input parameters (AccountId and ProductId). This is achieved by using the Additional Input property to define the key/value pairs. Merge fields (%...%) are used to pull values from the Integration Procedure's data JSON, including the nested ProductId. The Send Only Additional Input checkbox is then checked to ensure that only this newly constructed data is sent to the Apex method, rather than the entire original data JSON, which would not match the method's signature.

1. Salesforce Help

OmniStudio Documentation

Remote Action for Integration Procedures: This official documentation details the properties of the Remote Action element.

Additional Input: "Passes additional data to the Apex class method as key/value pairs. The keys are the input parameters for the method. The values can be literal values or merge fields from the data JSON." This directly supports using Additional Input to map the required fields.

Send Only Additional Input: "When checked

sends only the data in the Additional Input property to the remote call. When unchecked

sends the entire data JSON plus the Additional Input data." This confirms its role in sending a precise payload.

Send JSON Path: "Specifies a node in the data JSON to send to the remote call." This confirms it sends an entire node

which is not the requirement here.

2. Salesforce University Courseware

"Build Guided Experiences with OmniStudio": Module on Integration Procedures.

The courseware explains that when an external service or Apex method requires a specific

flat JSON structure

the combination of Additional Input (to create the structure) and Send Only Additional Input (to isolate it) is the standard and correct pattern. This aligns perfectly with the scenario described in the question.