> ## Documentation Index
> Fetch the complete documentation index at: https://nango-marcin-nan-6306-mcp-tool-connections-get.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

Use a Nango API key as a Bearer token in the `Authorization` header.

```
Authorization: Bearer <NANGO-API-KEY>
```

Nango has two API key types. They are not interchangeable:

* **[Environment API keys](/reference/backend/http-api/api-keys#environment-api-keys)** — access a single environment. Manage them under **Environment Settings > API Keys**. Each key has [scopes](/reference/backend/http-api/api-keys#scopes) that control which environment endpoints it can access. A key without the required scope receives a `403 Forbidden` response.
* **[Account API keys](/reference/backend/http-api/api-keys#account-api-keys)** — access account-level APIs only. Manage them from [Account API keys](https://app.nango.dev/api-keys) in the dashboard. They do not grant access to any environment.