Most of the time it’s hard to introduce usability to developers, they always start out by assuming it has something to do with GUI and that graphic stuff. After some discussion they see the value in usability but most of the time they need a lot more persuasion and argumentation before they accept that it has to be an integrated part of the development.
However, in this I have also found that developers are unknowingly starting to talk about usability, calling it something else. And when it comes to understanding and working with an API they can often relate to the concept of usability.
So what does this has to do with the agile manifesto as the title of this post says?
Well, a few well chosen words got the developer community to start thinking in new directions and it was a good and much needed change. But in my opinion they missed on a few things. So now it's time for the guys that stand behind the agile manifesto they start acting on their principals, especially the last one. With only a few small changes to the manifesto and the principles, you could push the agile community to be user-centric as well.
The first little change is Working software, it is far too vague. Changed it to Usable software, actually I think they had that in mind. (Oh no, something fluffy as usable, it's so much easier to test if something is working or not!). By using the working software terminology you loose on usability, working software in engineering terms can be far from usable.
Next is the word customer. To be able to reach the goal of usable software you have to talk to the users, not the customers. The word customers instead of users shift the focus totally. By using customer you lock on to older paradigms where someone acting as the customer or product owner or whatever is responsible for handling the requirements.
Well, actually if you would go through and update the manifesto with these two small fixes and adapted those principles in your agile methods. You would have gained a lot for the users, the ones that have to put up with your software.