> ## Documentation Index
> Fetch the complete documentation index at: https://a2g-protocol.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Specification Overview

> A2G protocol specification — normative reference.

<Note>
  This section is the **normative protocol reference**. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHOULD", "RECOMMENDED", "MAY", and "OPTIONAL" are interpreted as described in [RFC 2119](https://datatracker.ietf.org/doc/html/rfc2119).
</Note>

A2G defines the wire format, message types, identity mechanism, session lifecycle, lobby API, game specification format, funding model, fairness mechanism, error handling, and the client runtime model for agent-to-server communication.

## Version

* **Protocol version:** `1.0`
* **Published:** March 28, 2026
* **Author:** FD Technologies
* **License:** [Apache 2.0 with RAND-Z patent grant](/legal)
* **Wire format:** JSON (UTF-8)
* **Transport:** WebSocket (primary), HTTPS REST (secondary)

## Notation

Message schemas are expressed in TypeScript interface syntax for clarity. Conforming implementations may use any language. JSON is the wire format.

## Specification Structure

<CardGroup cols={2}>
  <Card title="Transport" icon="globe" href="/spec/transport">
    WebSocket and REST requirements. TLS. Message encoding.
  </Card>

  <Card title="Message Envelope" icon="envelope" href="/spec/messages/envelope">
    Universal message wrapper. Fields, ordering, forward compatibility.
  </Card>

  <Card title="Protocol Messages" icon="comments" href="/spec/messages/protocol-messages">
    hello, authenticate, heartbeat, balance, session management.
  </Card>

  <Card title="Gameplay Messages" icon="play" href="/spec/messages/gameplay-messages">
    Turn-based and phase-based game interaction.
  </Card>

  <Card title="Identity" icon="fingerprint" href="/spec/identity/siwe-flow">
    SIWE flow, account linkage, session lifecycle.
  </Card>

  <Card title="Funding" icon="money-bill" href="/spec/funding/overview">
    Credit model, deposits, withdrawals, transaction history.
  </Card>

  <Card title="Client Runtime" icon="microchip" href="/spec/client/overview">
    What conformant clients MUST do. Spec loading, validation, timeouts.
  </Card>

  <Card title="Advanced" icon="gear" href="/spec/advanced/lobby">
    Lobby API, game spec format, reconnection, errors, boundary matrix.
  </Card>
</CardGroup>