This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:561fc978-61f4-4545-bac8-3b1349e5a515

Content

Additionally, servers performing server to server delivery of the following activities MUST also provide the target property: Add, Remove.

Origin

prefix Servers performing delivery to the inbox or sharedInbox properties of actors on other servers MUST provide the object property in the activity: Create, Update, Delete, Follow, Add, Remove, Like, Block, Undo.

Additionally, servers performing server to server delivery of the following activities MUST also provide the target property: Add, Remove.
 
suffix HTTP caching mechanisms [RFC7234] SHOULD be respected when appropriate, both when receiving responses from other servers as well as sending responses to other servers.

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

JSON

{
  "id": "urn:uuid:561fc978-61f4-4545-bac8-3b1349e5a515",
  "uuid": "561fc978-61f4-4545-bac8-3b1349e5a515",
  "type": "Behavior",
  "content": "Additionally, servers performing server to server delivery of the following activities MUST also provide the target property: Add, Remove.\n",
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "Server to Server Interactions",
      "id": "https://www.w3.org/TR/activitypub/#server-to-server-interactions"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#server-to-server-interactions",
      "branch": [
        7
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "Servers performing delivery to the inbox or sharedInbox properties of actors on other servers MUST provide the object property in the activity: Create, Update, Delete, Follow, Add, Remove, Like, Block, Undo.\n",
      "exact": "Additionally, servers performing server to server delivery of the following activities MUST also provide the target property: Add, Remove.\n",
      "suffix": "HTTP caching mechanisms [RFC7234] SHOULD be respected when appropriate, both when receiving responses from other servers as well as sending responses to other servers.\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}