Index is a composable discovery protocol that allows to create truly personalized and autonomous discovery experiences across the web. Index provides a decentralized semantic index that eliminates data fragmentation, a composable discovery protocol that allows data to be queried from multiple sources, in a user-centric manner. On top of this, it provides a real-time environment for agents that facilitates integration with algorithms and services and ensures that information acquires a fluid, social, and autonomous structure. By storing vector embeddings on a decentralized knowledge graph, Index Network creates the first decentralized semantic index, introducing a new open layer to information discovery.