"Also, is there anything that works with TCL that makes it easy to jump to the definition of a proc? Does tags work with TCL?"
I'm not sure what you mean, exactly. It's easy to find out the definition of a Tcl procedure, what arguments it takes, etc. (Tcl's introspection facilities are great!).
info body proc_name will give you the source code for the proc, and
info args proc_name will tell you what arguments it takes.
(Or, did you mean something else, like the API browser?)