This is one of many protocol behaviors described in ActivityPub.

Identifier

urn:uuid:83a907d3-3c5d-4e1b-99b5-0a8b6efb67fd

Content

Servers MUST de-duplicate the final recipient list.

Origin

prefix Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.

Servers MUST de-duplicate the final recipient list.
 
suffix Servers MUST also exclude actors from the list which are the same as the actor of the Activity being notified about.

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

JSON

{
  "id": "urn:uuid:83a907d3-3c5d-4e1b-99b5-0a8b6efb67fd",
  "uuid": "83a907d3-3c5d-4e1b-99b5-0a8b6efb67fd",
  "type": "Behavior",
  "content": "Servers MUST de-duplicate the final recipient list.\n",
  "context": [
    "https://www.w3.org/TR/activitypub/",
    {
      "name": "7. Server to Server Interactions",
      "id": "https://www.w3.org/TR/activitypub/#server-to-server-interactions"
    },
    {
      "name": "7.1 Delivery",
      "id": "https://www.w3.org/TR/activitypub/#delivery"
    }
  ],
  "origin": {
    "source": "https://www.w3.org/TR/activitypub/",
    "section": {
      "id": "https://www.w3.org/TR/activitypub/#delivery",
      "branch": [
        7,
        1
      ]
    },
    "selector": {
      "type": "TextQuoteSelector",
      "prefix": "Servers MUST limit the number of layers of indirections through collections which will be performed, which MAY be one.\n",
      "exact": "Servers MUST de-duplicate the final recipient list.\n",
      "suffix": "Servers MUST also exclude actors from the list which are the same as the actor of the Activity being notified about.\n"
    }
  },
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://socialweb.coop/ns/testing/context.json"
  ]
}