One thing I really like it for is if you have a lot of something similar - let's say plugins. I can then just go to the plugins directory, and tell claude something as simple as "this is the plugins directory where plugins live. I want to add one called 'sample' that samples records". Note that I don't even have to tell it what that means usually.

It will read the existing plugins, understand the code style/structure/how they integrate, then create a plugin called "sample" AND code that is usually what you wanted without telling it specifically, and write 10 tests for it.

In those cases it's magic. In large codebases, asking it to add something into existing code or modify a behavior I've found it to be...less useful at.