From the website:
Chris Wanstrath and I originally developed Hurl for the 2009 Rails Rumble where it won Most Complete. The idea was to create a simple web version of cURL, a command-line tool often used to test web APIs.
Hurl is super easy – just enter a URL and any extra parameters such as HTTP headers, body parameters, and authentication and then click “Send.” You’ll get the response and can save and share it.
By open sourcing the code behind Hurl we hope that other developers will be able to build on the concept. One very requested feature is to create an embeddable version of Hurl that can be used in developer documentation for easy try-it functionality.
Not topic map specific but certainly will be useful for developers working on web APIs for topic map software.