An example activity that likes an article object:

{ "@context": ["https://www.w3.org/ns/activitystreams", {"@language": "en"}], "type": "Like", "actor": "https://dustycloud.org/christine/", "summary": "Christine liked 'Minimal ActivityPub update client'", "object": "https://rhiaro.co.uk/2016/05/minimal-activitypub", "to": ["https://rhiaro.co.uk/#amy", "https://dustycloud.org/followers", "https://rhiaro.co.uk/followers/"], "cc": "https://e14n.com/evan"}