The W3C Thing Description (TD) is a central building block in a Web of Things (WoT) enabled system and can be considered as the entry point of a Thing (aka the index.html of the Thing).

The TD consists of semantic metadata for the Thing itself, a narrow-waist interaction model with WoT's Properties, Actions, and Events, a semantic schema to make data models machine-understandable, and features for Web Linking to express relations among Things.