Recently I wanted to try a COOP scenario from the steam workshop which required several workshop mods and I assumed that there would be a way to get the server to download the workshop scenario so that if an update came out, the server could be restarted and it would automatically download the workshop content updates. UWD is probably the best 'It Just Works' we’ll get, so we hope you enjoy it.I use Firedaemon to start and stop servers and I use the Firedaemon pre-service feature to validate/update files before the server launches using steamcmd.

When new addons are added to the server only them will be scanned then cached with the others. Other than that we have a cache system that makes the loading process very fast! Once an addon is scanned for resources it’ll only be checked again after it gets an update. – Somethimes Workshop or the game themselves are buggy or misbehaving – contact GMod devs. – It’s not uncommon to see addons with improper tags, which can confuse UWD – The script doesn’t auto subscribe to missing addon requirements (you have to be sure your server has everything that’s needed by ALL addons) – UWD can’t deal with game contents (you still have to buy and activate CSS) – Some addons will just be buggy and not fully load by themselves – contact their creators

We say 'most errors' and not 'all errors' because:

This process will make everybody see the server contents correctly, so most ERRORs ( missing models) and black and purple textures ( missing textures) will be 'fixed' without the need of manually subscribing to tons of addons! It checks for the current gamemode (if it’s a custom one), the current map (and its contents), addons with important resources (such as mdl, vtf, vcd, wav, mp3, ogg, vmt, vtf, png and ttf) and even validates your pointshop models! When playing on a server, this script makes people automatically download a selection of your mounted items from workshop.

Steam workshop downloader gmod