"viable instrument" is correct and usable in written English.
You can use it when describing something that has the potential to be effective or successful. For example, "This new approach to education provides a viable instrument for improving student learning."
DIZZY'S CLUB COCA-COLA Broadway at 60th St. (212-258-9595) — Sept. 1-2: In Edmar Castaneda's hands, the Colombian harp becomes a viable instrument for jazz improvisation.
Two Army officers, one of them Pinochet's grandson Augusto Pinochet III, demonstrated sympathy for Pinochet during the funeral, expressing their political affinity with a coup as a viable instrument.
The reported findings indicate that inkjet printing could be a viable instrument for the easy construction of a working biosensor via direct digital design using biological and conductive polymer based inks.
The Argonne fragment mass analyzer (FMA) has been a very important component of the experimental program at the ATLAS facility for many years and is expected to be a viable instrument for experiments with more intense beams which will become available when the ATLAS intensity upgrade is completed.
Therefore, it seemed a viable instrument to evaluate construct validity.
Thus, personal experience naturally functions as a viable instrument for risk perception.
Russian policy was at an impasse, without any viable instruments to restrict the westward drift of Ukraine, making the situation totally different from that of 2004.
Muscle force can be quantified by several viable instruments.
These results suggest that it may be feasible to combine the imaging and therapeutic capabilities into a single device as a clinically-viable instrument.
In Georgia, the European Union leadership could neither negotiate a clear, coherent, and viable ceasefire instrument, nor make Russia observe it.
The spatial policies at local level, although not directly linked to climate change, if implemented effectively may become a viable policy instrument to mitigate and adapt to climate change issues.
