Use Postman with the Web API
There are a number of third-party tools that allow you to authenticate to Dynamics 365 for Customer Engagement app instances and to compose and send Web API requests and view responses. Postman is one of the most popular.
Use Postman to perform ad hoc queries or to verify the behavior of operations without writing a program. This section covers information on how to configure a Postman environment that connects to your Dynamics 365 for Customer Engagement apps instance and use Postman to perform operations with the Web API.
This topic and its sub-topics contain information that is applicable only for the on-premises users of Customer Engagement apps.
The documentation that is applicable to Dynamics 365 for Customer Engagement app (online) users is now available in the PowerApps documentation at: Use Postman with Common Data Service Web API.
Postman offers many other capabilities beyond those covered in this content. More information: First 5 things to try if you’re new to Postman