This chapter shows how to extend Tornado tools by adding new procedures and capabilities to the Tornado shell and how to run a new procedure from the browser. The primary tool for developing these extended capabilities is wtxtcl, the Tcl binding to the WTX API. Most Tornado tools are implemented using Tcl, and it is straightforward to add function using Tcl as well. This chapter assumes familiarity with the material in 4.4 WTX Tcl API.