RCC/Websocket API - Field used for close price contribution

I'm using RCC via Websocket API to post Equity Indices data to Refinitiv, using python.

I'm able to connect to UAT correctly and it seems that the data went through

SENT:
{
  "Ack":true,
  "ID":1,
  "Key":{
    "Name":".FCIWD800USDP",
    "Service":"DDS_TRCE"
  },
  "Message":{
    "Fields":{
      "ASK":2284.0247,
      "DSPLY_NAME":"Hello RCC",
      "PRIMACT_1":106,
      "SEC_ACT_1":26
    },
    "ID":0,
    "Type":"Update"
  },
  "PostID":7,
  "Type":"Post"
}
RECEIVED: 
[
  {
    "AckID":7,
    "ID":1,
    "Type":"Ack"
  }
]

Now to contribute close price / last price what would be the best field to use ?

Having a field list documentation would be helpful

I've looked into the Websocket API Protocol Specification but I can't find it there (https://developers.lseg.com/content/dam/devportal/refinitivrealtimeapi_pdfs/websocket_api_protocol_specification.pdf)

Thanks for your help