This isn't a pure Chrome Extension, it just takes you to the site: https://suite.websecurify.com/rest

One of the main uses of a rest client in a chrome extension (e.g. postman/advanced REST client) is so you can use it offline. The entire functionality of the webpage is written in JS (https://suite.websecurify.com/rest/script) so it could be easily packaged into a true chrome extension, frankly as it stands this seems to be a bit of a half arsed attempt to get more exposure.