The json-to-xml policy in the IBM DataPower API Gateway operates on an in-memory representation of JSON data, not on a raw JSON string or stream. The official IBM documentation explicitly states that the input for this policy must be parsed JSON. If the preceding policy in the assembly (such as an invoke policy) does not provide a parsed JSON object in the specified context variable (by default, message.body), a parse policy must be used beforehand to convert the raw JSON payload into the required parsed format. This ensures the json-to-xml policy can correctly traverse the JSON structure to perform the conversion to XML (specifically, JSONx).

1. IBM Documentation for API Connect Version 10.0.x: In the documentation for the json-to-xml assembly policy

the "Description" section states: "The input to the policy is read from the variable that is specified in the input-variable field

or from message.body if an input variable is not specified. The input must be parsed JSON."

Source: IBM. (2023). API Connect Version 10.0.x Documentation. Section: "API-defining and processing policies" -> "json-to-xml". (Direct link varies

but this path is consistent in the IBM Knowledge Center/Documentation).