Facebook has a feature that has a few different names: "usage stories," "playing stories," "discovery stories," and "social discovery."
The idea is simple: when somebody starts using your FB app, FB automatically posts a "usage story" to the ticker, e.g. "Dan used BranchOut" or, if it's a game, "Dan played Candy Crush Saga." (They disappear quickly, but they're great for FB "Sponsored Stories" advertisements; you can also use them to add friendly faces to FB "Mobile App Install" ads.)
There's a setting for "Social Discovery" on the Facebook app "Advanced" settings page, enabled by default, but it's in the "App Restrictions" section; I think that's only how you force it off. Leaving it "On" doesn't actually generate those stories.
My question is: what are the minimum requirements to publish usage stories? Does the app have to have a Canvas URL? Does it require an App Center details page? Can my off-Facebook website publish usage stories? Can native mobile apps publish usage stories? (Can apps that are mobile-only get usage stories?) Can I publish usage stories myself using the Graph API? What are the requirements?