> For the complete documentation index, see [llms.txt](https://docs.appmixer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.appmixer.com/6.0/v4.2/appmixer-sdk/api-reference/constructor.md).

# Constructor

## Appmixer

| Method                                      | Description                                                                                                                                                                                                                                                       |
| ------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `Appmixer({ baseUrl })`                     | A constructor function to create an instance of the Appmixer SDK. Pass the base URL of the engine (Appmixer API).                                                                                                                                                 |
| `appmixer.set(key, value)`                  | Set a property on the appmixer SDK object. Currently only `accessToken` should be set to be able to make calls to the Appmixer API.                                                                                                                               |
| `appmixer.onInvalidAccessToken(callbackFn)` | Allows setting a callback function that will be called whenever the current access token on the SDK is not valid. More information can be found on the [Managing Authentication ](/6.0/v4.2/tutorials/managing-authentication.md#check-token-expiration)tutorial. |


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