Most API methods return results in JSON format (application/json). Furthermore, there is support for results in CSV and PDF format as long as the result of the respective API method is declared as exportable (with the AllowExport flag). Basically, an API method can return results in any format compatible with HTTP.
To obtain results in CSV format
In the query, set Accept header to text/csv.
To obtain results in PDF format
In the query, set Accept header to applciation/pdf.
NOTE: To obtain results in PDF format, the RPS module must be installed on your system.