# SendMessage (Publish)


Sends a message to participants of the room.

## Required Capability


`SEND_MESSAGE`

## Format


```
{
  "Action": "SEND_MESSAGE",
  "Attributes": {
    "user_id": "string",
    "display_name": "string"
  },
  "Content": "string",
  "RequestId": "string"
}
```

## Fields



| Field | Required | Description | 
| --- | --- | --- | 
| `Action` | Yes | `SEND_MESSAGE` | 
| `Attributes` | No | Details of the event; e.g., `user_id`, `display_name`, and/or anything you want. | 
| `Content` | Yes | Message to send. The character length of this field must be shorter than the room’s configured `maximumMessageLength`. Maximum: 500 unicode code points. | 
| `RequestId` | No | An identifier optionally specified by your application for tracking purposes. If specified, this appears in corresponding subscribe operations. |