> For the complete documentation index, see [llms.txt](https://docs.tsgglobal.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tsgglobal.com/api-reference/programmable-sms/smpp/headers.md).

# Headers

## Authentication

{% hint style="info" %}
Authentication is done by passing your TSG Global API key via the Authorization header in the format "Authorization: Bearer \<api\_key>"
{% endhint %}

## Parameters & Content-Type

Parameters should be JSON encoded and passed in the request body (with the Content-Type header set to `application/json`). IDs are always UUIDv4. Timestamps are in the ISO8601 format and in UTC.

## <br>