Talend API Tester - Free Edition, formerly known as Restlet Client, is a powerful tool for visually interacting with REST, SOAP, and HTTP APIs. It provides a user-friendly interface that makes it easy to invoke, discover, and test APIs.

With Talend API Tester - Free Edition, you can send requests and inspect responses, regardless of their complexity. The tool supports dynamic requests by allowing you to insert variables. It also provides full support for security, authentication, hypermedia, and HTML forms. Additionally, you can visualize, prettify, and inspect HTTP responses.

One of the key features of Talend API Tester - Free Edition is the ability to validate API behavior. Whether you want to ensure that your API is behaving as specified or test third-party APIs, you can perform various API response tests. The tool allows you to use assertions to validate values of headers, parts of the body, or response time. You can also create environment variables to increase the reusability of your tests.

Other notable features include the ability to view and search your call history, edit and re-send requests from history, save and organize requests into projects and services, build dynamic requests with custom variables, security, and authentication, visualize and inspect responses in different formats (JSON, XML, HTML, images), and validate responses with assertions.

Talend API Tester - Free Edition also offers easy import options for Postman Collections, Swagger / OAS / OpenAPI, and HAR (HTTP Archive).

Please note that Talend API Tester requires certain permissions such as "Read and change all your data on the websites you visit" and "Communicate with cooperating websites" in order to function properly. These permissions are necessary for the tool to access internet resources and perform its intended functions.