---
url: 'https://adk.nht.io/api/@nhtio/adk/common/type-aliases/MessageRole.md'
description: 'The roles a [`Message`](https://adk.nht.io/api/@nhtio/adk/common/classes/Message) author can hold.'
---

# Type Alias: MessageRole

```ts
type MessageRole = "user" | "assistant";
```

Defined in: [lib/classes/message.ts:18](https://github.com/NHTIO/ADK/blob/v1.20260605.0/src/lib/classes/message.ts#L18)

The roles a [Message](../classes/Message.md) author can hold.

## Remarks

Restricted to `user` and `assistant` — system instructions, developer directives, and
tool results are handled separately and never appear in the persisted message history.