At the company I work for, we have not yet adopted a final methodology for us to use, and we are thinking of adopting agile development in the next projects.
What would an agile process look like? Do I need to create a requirements document with every specification in detail or can I describe it in a
readme.md and use user stories to generate our interactions along with Scrum?
The Agile Manifesto values the following items:
Individuals and interaction between them more than processes and tools
Software at work more than comprehensive documentation
Collaboration with the client more than negotiating contracts
Responding to Changes More Than Following a Plan
It is important to make it clear that the items on the right are not less necessary, they are just less important than the items on the left.
The manifesto still has its principles , but the main idea behind it is to work where conventional models fail most.
Set aside very specific documentation (which often tells how the programmer should do their job), encourage communication between team members as much as possible (with daily meetings), understand what the customer wants and have constant feedback and embrace change constant , whether changes in requirements or changes to bring improvements to the team.
Trying to answer your question: no matter how you do your documentation , just don't waste too much time on it . Worry more about understanding what the customer wants and conveying it to the rest of the team (even if it is not necessary to put the team and the customer in the same room), whether in the format of user stories, in a Word document, a file of text or multiple Post-its organized by the room.
As I mentioned before, the Agile Manifesto has a lot of principles and all of this can seem very abstract on paper.
That's why I highly recommend that you watch these videos about Extreme Programming , by Vinícius Teles at TDC 2008. I'm not recommending that you apply Extreme Programming, but I think Vinícius' explanation (and his great and hilarious analogies) can help you a lot, as well as helped me.