Documentation isn’t ready yet, but here’s some example links to get you started.
https://api.guildwars2.com/v2/recipes/2869
https://api.guildwars2.com/v2/recipes/9716
https://api.guildwars2.com/v2/recipes/search?input=12138
https://api.guildwars2.com/v2/recipes/search?output=45656