> Fetch clean Markdown by appending `.md` to any page URL under https://signalwire.com/docs or requesting it with the HTTP header `Accept: text/markdown`. The root index at https://signalwire.com/docs/llms.txt lists the available documentation indexes.

# setAllowedEnvPrefixes

> Set the allowed environment variable prefixes for this DataMap instance.

[ref-datamap]: /docs/server-sdks/reference/typescript/agents/data-map

Set the allowed environment variable prefixes for this DataMap instance.
Overrides the global defaults. Only env vars whose names start with one of
these prefixes will be expanded. An empty array allows all variables.

## **Parameters**

**`prefixes`** `string[]` — required

Array of prefix strings to allow.

---

## **Returns**

[`DataMap`][ref-datamap] -- Self for method chaining.

## **Example**

```typescript {5}
import { DataMap } from '@signalwire/sdk';

const dm = new DataMap('get_weather');
dm.enableEnvExpansion();
dm.setAllowedEnvPrefixes(['WEATHER_', 'APP_']);
dm.webhook('GET', 'https://api.weather.com/v1/current?key=${ENV.WEATHER_API_KEY}');
```

> Set the allowed environment variable prefixes for this DataMap instance.