# Prerequisites and overview for using Guard rules
<a name="getting-started"></a>

This section demonstrates how you can complete the core Guard tasks of writing, testing, and validating rules against JSON- or YAML-formatted data. In addition, it contains detailed walkthroughs that demonstrate writing rules that respond to specific use cases.

**Topics**
+ [Prerequisites](#getting-started-prerequisites)
+ [Overview of using Guard rules](#getting-started-overview)
+ [Writing AWS CloudFormation Guard rules](writing-rules.md)
+ [Testing AWS CloudFormation Guard rules](testing-rules.md)
+ [Using input parameters with AWS CloudFormation Guard rules](using-input-parameters.md)
+ [Validating input data against AWS CloudFormation Guard rules](validating-rules.md)

## Prerequisites
<a name="getting-started-prerequisites"></a>

Before you can write policy rules using the Guard domain-specific language (DSL), you must install the Guard command line interface (CLI). For more information, see [Setting up Guard](setting-up.md).

## Overview of using Guard rules
<a name="getting-started-overview"></a>

When using Guard, you typically perform the following steps:

1. Write JSON- or YAML-formatted data to validate.

1. Write Guard policy rules. For more information, see [Writing Guard rules](writing-rules.md).

1. Verify that your rules work as intended by using the Guard `test` command. For more information about unit testing, see [Testing Guard rules](testing-rules.md).

1. Use the Guard `validate` command to validate your JSON- or YAML-formatted data against your rules. For more information, see [Validating input data against Guard rules](validating-rules.md).