Hi @jonschlinkert,

Step parameters in most cases can contain actual values or placeholders for values, as well as specifying how the parameter should be mapped into a particular API operation (when applicable). In the placeholder situation the value is normally expressed in the form of a runtime expression to be evaluated by tooling parsing/processing the Arazzo Description). The expression could specify that the value will be taken from provided workflow inputs, or perhaps from previous steps within a given workflow.

If you want to pass arguments into a workflow, then you would define the shape of the inputs using JSON Schema (see Workflow inputs fixed field).

If you have a concrete example, I can try to answer more explicitly for you.