What is A2X?

A2X is a TypeScript SDK for building and consuming A2A (Agent-to-Agent) protocol agents. It lets you expose any LLM-backed workflow as a standards-compliant endpoint other agents and clients can discover, call, and stream from.

Mental model

An A2A agent is an HTTP service with two surfaces:

• GET /.well-known/agent.json — a discoverable AgentCard that describes what the agent can do, how to authenticate, and how to reach it.
• POST /a2a — a JSON-RPC endpoint that accepts message/send, message/stream, tasks/get, and tasks/cancel.

A2X gives you two things:

1. Server-side ergonomics — define your agent in plain TypeScript, plug in an LLM provider, and A2X emits a correct AgentCard and wires up the JSON-RPC handler for you.
2. Client-side ergonomics — A2XClient calls any A2A-compliant agent (not just A2X ones) with a typed, Promise/AsyncIterator surface.

When to reach for A2X

• You want to expose an LLM workflow as an A2A endpoint without hand-authoring AgentCards.
• You want to compose agents (delegation, pipelines, parallel fan-out, iterative refinement).
• You want to call third-party A2A agents from TypeScript code with type safety.
• You want to stay framework-agnostic — A2X plugs into Express, Fastify, Hono, Next.js, or any Node.js HTTP stack.

When A2X is overkill

• You're calling a single LLM once and don't need discovery, streaming, or multi-agent composition. Use the provider SDK directly.
• You need a UI framework — A2X is a protocol layer, not a frontend.

What's next

• Quickstart — your first agent in under 30 lines of code.
• Agent guides — the primary path for building agents.
• Client guides — consuming remote A2A agents.