When building a language there is one aspect which is absolutely crucial: that is tool support.
Tool support will determine if your language is usable at all, it will influence the reception from user and the usability.
In this video I explain why and how you can build great tool support with a limited effort.

Tool support is what makes a real language. This is also one of the reasons why I am against the whole concept of internal DSLs: they are nice but they are not really languages. They cannot be compared in any way to external DSLs (a.k.a. real DSLs).

And it is nice that experts agree on this: