The prototype and a documentation comment need to go in `include/phenom/string.h`; this is needed for two reasons:

* The compilation flags for libphenom are intentionally very strict: without a function prototype in the header, the build won't succeed.  Function prototypes are very important on 64-bit platforms, as they affect register allocation and missing prototypes can result in broken executables

* The docs on the website are built from the documentation comments in the header.  Without the docs, it is difficult for folks to discover and use your new API functions.

Take a look at the other docs in `include/phenom/string.h` for examples on the convention and styling of docs