# `Twilio.Api.V2010.Call.UserDefinedMessageService`
[🔗](https://github.com/jeffhuen/twilio_elixir/blob/main/lib/twilio/api/v2010/call/user_defined_message_service.ex#L2)

Allows your server-side application to send messages to the Voice SDK end user during an active Call.

Operations: `create`

# `create`

```elixir
@spec create(Twilio.Client.t(), String.t(), map(), keyword()) ::
  {:ok, Twilio.Resources.Api.V2010.Call.UserDefinedMessage.t()}
  | {:ok, map(), map()}
  | :ok
  | {:error, Twilio.Error.t()}
```

Create a new User Defined Message for the given Call SID.

Operation: `CreateUserDefinedMessage` | Tags: Api20100401UserDefinedMessage

## Required Parameters

| Parameter | Type | Description |
|-----------|------|-------------|
| `Content` | string | The User Defined Message in the form of URL-encoded JSON string. |
## Optional Parameters

| Parameter | Type | Description |
|-----------|------|-------------|
# credo:disable-for-next-line Credo.Check.Readability.MaxLineLength
| `IdempotencyKey` | string | A unique string value to identify API call. This should be a unique string value per API call and can be a randomly generated. |

---

*Consult [api-reference.md](api-reference.md) for complete listing*