server_to_client.json: This is the core, catalog-agnostic schema for messages sent from the server to the client. It defines the four main message types (beginRendering, surfaceUpdate, dataModelUpdate, deleteSurface) and their structure. In this schema, the component object within a surfaceUpdate message is generic ("additionalProperties": true), allowing any component definitions to be passed.
client_to_server.json: This schema defines the structure for event messages sent from the client to the server. This includes user-initiated actions (userAction), error reporting (error), and the crucial clientUiCapabilities message, which allows a client to inform the server about the component catalog it supports.
catalog_description_schema.json: This is a meta-schema that defines the structure of an A2UI component catalog. A catalog consists of a components object and a styles object, where each key is a component/style name and the value is a JSON schema defining its properties. This allows for the creation of custom component sets.
standard_catalog_definition.json: This file is a concrete implementation of a catalog, conforming to the catalog_description_schema.json. It defines the standard set of components (e.g., Text, Image, Row, Card) and styles that are part of the baseline A2UI specification.
server_to_client_with_standard_catalog.json: This is a resolved, LLM-friendly version of the server-to-client schema. It is generated by combining server_to_client.json with the standard_catalog_definition.json. In this version, the generic component object is replaced with a strict oneOf definition that includes every component from the standard catalog. This provides a complete, strictly-typed schema that is ideal for LLMs to use for generating valid A2UI messages without ambiguity.