User stories are a part of every agile driven process that teams usually follow.
Often, even a developer can be called to write a story, based on a business requirement, that will eventually be called to develop it. Here's an example:
As a Developer, I want to be able to filter Blog Posts by Category ID, so I can display a filtered table.
But one can easily be distracted and write a story based on their understanding of how consumers are using their code. Much like product owners.
Before you start, talk to your consumers. See how their are using your code or your REST API. Ask them for feedback and for possible hard times they have with it.
Then, write your user stories, based on that.