The Open Databases Integration for Materials Design (OPTIMADE) consortium aims to make materials databases interoperational by developing a common REST API. This repository contains the specification of the OPTIMADE API. optimade.rst: The API specification. AUTHORS: List of contributors. optimade.org: Public OPTIMADE web site OPTIMADE wiki: Information for developers The subdirectory schemas/ contains OpenAPI schemas for the main OPTIMADE API and index meta-database as implemented by the optimade-python-tools repository. Note: These schemas are an approximation of the full human-readable specification and may be missing certain constraints. Furthermore, they may not be up to date in the develop branch of this repository.