From declaration to page: the explanation →

From Declaration to Page

One Union type.Every interaction, such as requests and replies, in one place.Declare it once.People get a page. AI gets a tool. Programs get a library.Not the Web.The full web experience with native UI, from a few bytes of data.

The App

The developer's code: one Union type holds every interaction

The App never reads a schema. Generated code encodes and decodes its values, whoever sent them.

The data

What crosses between them

Who uses it

The client has the schema, so it understands and draws

A conceptual drawing of the page, not a product screenshot. Each client lays out the same schema in its own native controls.

The Hub turns each request into a tool, named and described by the declaration and its comments

The AI calls it with

The Hub encodes

Generated from the Rust declaration, shown abridged; the explanation page has it in full. A null for a field that is not Nullable cannot be encoded, and the Hub rejects the call.

Another App uses the same declared types and the SDK

The SDK encodes

interview is the other App's Endpoint for this protocol, connected to this App when its task is configured.

Keyboard: ← and → change steps, Space plays or pauses, Home starts over.

The bytes are the exact Avro encoding of each value, as the Rust SDK produces it: the variant index first, then the fields in order. A TypeScript App sends the same bytes; its kind field is the variant index, written once. A tool call and an SDK request carry the same value. Only the value is shown, not the transport that carries it.