The "Tools" Lesson is part of the full, Elm course featured in this preview video. Here's what you'd learn in this lesson:
The first tool accepts HTML and returns Elm Html. The second tool accepts JSON and returns Elm type alias and decoders and encoders. The third tool lists compiler error messages. The fourth tool generates boilerplate Elm application code. The fifth tool is a pretty print for Elm code. The sixth tool is built into the latest version of ELM and is a history of messages that map to each change of application state. The seventh tool lets you define your CSS in Elm.