There are lots of commercially available controls for application to trouble spots, but all are temporary. Moss grows in areas of low fertility, acidic soil conditions, poor drainage, where soil is compacted, heavy shade, restricted air movement, or a combination of the preceding. Review the list & correct conditions that favor moss to rid your lawn of it. Sounds easy, but it's often a problem to correct some of the cultural conditions on the list. Perhaps one or two will stand out as the probable cause. I hope you're able to correct the problem.

Al

Why would you want to get rid of it? I think it would only add to the charm and rustic nature of the farmyard. (Just my humble opinion)
Cheers,
Dee.

A photo would be helpful, but I'm wondering if your gravel courtyard isn't a bit low compared to the surrounding ground. Would adding more gravel and increasing the depth be a possibility; I'm picturing raising the level of the stone above the damp area that is providing a foothold for moss/algae.

Note: Moss and algae underfoot are charming in theory, but not to those who have slipped/slid around on it in Fall and Winter