# Spec guidance
source: https://developer.mastercard.com/mastercard-send-account-info/documentation/spec-guidance/index.md

For guidance on the API specification's **Execute** button, see [Sandbox Testing](https://developer.mastercard.com/mastercard-send-account-info/documentation/spec-guidance/index.md#sandbox-testing).
Tip: Guidance for the API sections below:
The expandable API sections below are rendered from the API specification, which you can download using **Download spec**.

Each API call type is a section. Expand it to see the request parameters and example JSON body payload and/or example response for that call. There may be multiple examples, which may not show all possible fields. If so, select **All fields** to see the possible fields:

![](https://static.developer.mastercard.com/content/mastercard-send-account-info/documentation/img/example-selection-ai.png)

To see the field descriptions, click **Model** and expand the object/array blocks to show their contents.

**Request URI** shows the call's endpoint path based on the selected environment (for example, Sandbox URL).

You can edit the example payload. Switching to the Model view will reset the payload to the default example.
The API specification identifies the required (mandatory) API fields as per Mastercard Send API validation and systems. In the expandable sections below, these fields are indicated as follows:

* REQUIRED indicates a required parameter, for example:

![](https://static.developer.mastercard.com/content/mastercard-send-account-info/documentation/img/required-param.png)

* In the **Model** section, a red asterisk \* indicates a required object/array and **required: yes** indicates a required item, for example:

![](https://static.developer.mastercard.com/content/mastercard-send-account-info/documentation/img/required-item.png)

If an item is marked as required but its parent object/array is not, you only need to provide that item if you provide the parent.

The required indicator relates to general API validation. Some conditional fields might be required depending on the payment type, region, and so on. Some of the other optional fields might also be required as per program or network rules.