> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tesouro.com/llms.txt
> Use this file to discover all available pages before exploring further.

# API concepts

> Overview of the Tesouro FinOps API including OpenAPI specification, base concepts, and SDK generation resources.

This page gives you a general overview of base concepts we use in the Tesouro API.

## OpenAPI

Tesouro API specification is available in the OpenAPI 3.1 format.
You can use it to generate your own SDKs for integrating with the Tesouro API.

<Download src="/schemas/rest/openapi.json" filename="tesouro-openapi-v2025-06-23.json">
  <Button intent="primary">Download OpenAPI</Button>
</Download>

## Authentication

All API requests to the Tesouro API platform must be made over HTTPS. Calls made over plain HTTP will fail.

For more information on our authentication mechanism, see [Authentication](/finops/guides/authentication/overview).

## HTTP methods

Tesouro services follow the standard [CRUD](https://en.wikipedia.org/wiki/Create,_read,_update_and_delete) resource models. This maps to the standard HTTP verbs:

| HTTP method | Description                                                                |
| ----------- | -------------------------------------------------------------------------- |
| `GET`       | To retrieve a resource, or a collection of resources.                      |
| `POST`      | To create a new resource, or to execute a complex operation on a resource. |
| `PATCH`     | To update a resource partially.                                            |
| `PUT`       | To update a resource by providing a full replacement representation.       |
| `DELETE`    | To delete a resource.                                                      |

## Date and time

Timestamps are returned in UTC and formatted as `YYYY-MM-DDThh:mm:ss[.zzzzzz][Z|±hh:mm]` ([ISO 8601](https://de.wikipedia.org/wiki/ISO_8601)).

Dates without the time part are formatted as `YYYY-MM-DD`.