What is an adverb for brevity?

There isn't a single perfect adverb for "brevity" in the sense of "being brief". However, depending on the context, you could use:

For conciseness:

* Briefly

* Succinctly

* Concisely

* Compactly

* Tersely

* Abruptly (can have a negative connotation of being rude)

For shortness:

* Shortly

* Quickly

* Rapidly

* Summarily

For directness:

* Point-blank (often used for directness in speech)

The best choice will depend on the specific nuance you want to convey. For example, "briefly" implies a short duration, while "succinctly" focuses on the quality of being concise and to the point.