This question is going to be hard to answer, and i suspect that many non-programmers will have a hard time figuring out what would be a reasonable request.
Let me try to give some thoughts, and anyone else can jump in and offer their 2 cents.
A commandline tool without a graphical user interface, is always going to be much faster to code, plus they are more easily coded in any language and easier to make cross platform compatible.
Certain programming languages are more suitable than others for very rapid development. So-called RAD tools like delphi, visual basic are going to be well suited for coding GUI apps very rapidly. Scripting languages like perl and python are also good candidates for rapidly coding powerful small programs (though less suitable for gui stuff). Such tools can make it possible to code programs that need to do things like connect to the web, using libraries and components.
A major issue that will affect whether a request can be coded quickly will be the extent to which the programmer already has some partial code that does some part of the request.
In short, the best approach is to think small, and expect that the coder may have to make some compromises and refine your suggestions to narrow the scope of the program to something that is achievable in a short timeframe.