Some walks will say that they are one way only - sections of long distance paths as standard, and anything which says in its name that it is from X to Y, where the summary will probably start 'This linear walk....' (e.g.
https://www.walkhighlands.co.uk/lothian/dalmeny-estate.shtml)
Highland ridge walks aren't necessarily as clearly labelled, though - the Aonach Eagach description doesn't admit until the last line that you still have to get back to the start on your own! I think if you look at one of these you're expected to already know what you're letting yourself in for...