matrix-spec/event-schemas/schema/v1/m.room.member

{
    "type": "object",
    "title": "The current membership state of a user in the room.",
    "description": "Adjusts the membership state for a user in a room. It is preferable to use the membership APIs (``/rooms/<room id>/invite`` etc) when performing membership actions rather than adjusting the state directly as there are a restricted set of valid transformations. For example, user A cannot force user B to join a room, and trying to force this state change directly will fail.",
    "allOf": [{
        "$ref": "core-event-schema/state_event.json"
    }],
    "properties": {
        "content": {
            "type": "object",
            "properties": {
                "membership": {
                    "type": "string",
                    "description": "The membership state of the user.",
                    "enum": ["invite","join","knock","leave","ban"]
                },
                "avatar_url": {
                    "type": "string",
                    "description": "The avatar URL for this user, if any. This is added by the homeserver."
                },
                "displayname": {
                    "type": ["string", "null"],
                    "description": "The display name for this user, if any. This is added by the homeserver."
                }
            },
            "required": ["membership"]
        },
        "state_key": {
            "type": "string",
            "description": "The ``user_id`` this membership event relates to."
        },
        "type": {
            "type": "string",
            "enum": ["m.room.member"]
        }
    }
}