This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:7eb99a13-a30d-43c8-ba13-01d11ee3dc00

Content

Clients submitting [some] activities to an outbox MUST provide the object property in the activity

Origin

prefix The receiving outbox can then perform delivery to not only the followers of Chris (the liker), but also to Amy, and Amy's followers and Evan, both of whom received the original article.

Clients submitting the following activities to an outbox MUST provide the object property in the activity: Create, Update, Delete, Follow, Add, Remove, Like, Block, Undo.
 
suffix Additionally, clients submitting the following activities to an outbox MUST also provide the target property: Add, Remove.

https://www.w3.org/TR/activitypub/

JSON

{
  "id": "urn:uuid:7eb99a13-a30d-43c8-ba13-01d11ee3dc00",
  "uuid": "7eb99a13-a30d-43c8-ba13-01d11ee3dc00",
  "type": "Behavior",
  "content": "Clients submitting [some] activities to an outbox MUST provide the object property in the activity",
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "Client to Server interactions",
      "id": "https://www.w3.org/TR/activitypub/#client-to-server-interactions"
    },
    {
      "name": "Client Addressing",
      "id": "https://www.w3.org/TR/activitypub/#client-addressing"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#client-addressing",
      "name": "Client Addressing",
      "branch": [
        6,
        1
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "The receiving outbox can then perform delivery to not only the followers of Chris (the liker), but also to Amy, and Amy's followers and Evan, both of whom received the original article.\n",
      "exact": "Clients submitting the following activities to an outbox MUST provide the object property in the activity: Create, Update, Delete, Follow, Add, Remove, Like, Block, Undo.\n",
      "suffix": "Additionally, clients submitting the following activities to an outbox MUST also provide the target property: Add, Remove.\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}