There's nothing strange in this domain about relying on people to read the C header. On a running system `man syscall` points you to sys/syscall.h. Read /usr/include/sys/syscall.h which says it gets the actual numbers from kernel header asm/unistd.h. Read that and it redirects in simple if-else fashion to the specific header, e.g., asm/unistd_64.h. That file is clear as day:

    #ifndef _ASM_UNISTD_64_H
    #define _ASM_UNISTD_64_H

    #define __NR_read 0
    #define __NR_write 1
    #define __NR_open 2
    ...
    #endif /* _ASM_UNISTD_64_H */

That was all on my x86-64 machine. Same again on an aarch64:

    #define __NR_io_setup 0                                                                                                               
    #define __NR_io_destroy 1                                                                                                             
    #define __NR_io_submit 2 
    ...

I'm not saying that wanting a table on the web or a spreadsheet or whatever is bad or wrong, but it is not a difficult or obtuse task. I think people who write code that does such things are generally familiar with just reading some C headers, or if they're already using C they just `#include <sys/syscall.h>` and call it a day.

Then on the calling convention, etc., the nolibc project (in the kernel tree) is great for learning or smaller projects (but of course Agner Fog's docs are the "canon" there).