I went through the REST API tutorial 9 for creating instrument list.
However, I was wondering if you can create an instrument list from scratch by importing via API a large instrument list in the same way as the GUI or FTP.
You can import instrument list from CSV or XML file using ImportFromBytes endpoint. The imported bytes data is in base64 format, so application needs to read data from file and convert it to base64 format first. For example code and message, please see the Import: XML and Import:Csv example in the "C# Example Application" in download page.