> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agenticenv.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# A2A Server

> Run an inbound A2A HTTP server with an agent card and JSON-RPC endpoint via RunA2A

Exposes the agent as an **inbound** [A2A](https://github.com/a2aproject/A2A) server — agent card at `/.well-known/agent-card.json` and JSON-RPC on `POST /` (PascalCase methods such as `SendMessage`, `SendStreamingMessage`).

Source: [`examples/agent_with_a2a_server/`](https://github.com/agenticenv/agent-sdk-go/tree/main/examples/agent_with_a2a_server)

## What it demonstrates

* `WithA2ADefaultServer` or `WithA2AServer` with host, port, bearer tokens
* `RunA2A(ctx)` blocking until shutdown
* Pair with [A2A Config](/examples/a2a-config) as a client

## Run

From `examples/`:

```bash theme={null}
go run ./agent_with_a2a_server
```

The process prints the **base URL** and **agent card URL** to stderr. **Ctrl+C** to stop.

Defaults: `localhost:9999` — override with `A2A_SERVER_HOST`, `A2A_SERVER_PORT` (see [Configuration](/examples/configuration)).

Optional **`A2A_SERVER_BEARER_TOKENS`** — comma-separated secrets; JSON-RPC calls must send `Authorization: Bearer <token>`. Agent card GET stays unauthenticated.

## Quick checks

```bash theme={null}
curl -sS "http://localhost:9999/.well-known/agent-card.json" | head
```

## Test as a client from this repo

Second terminal, `examples/`:

```bash theme={null}
export A2A_URL=http://localhost:9999
go run ./agent_with_a2a_config "What tools do you have?"
```

## Test with the `a2a` CLI

```bash theme={null}
go install github.com/a2aproject/a2a-go/v2/cmd/a2a@latest

a2a discover http://localhost:9999
a2a send http://localhost:9999 "Hello, what can you do?"
```

With bearer tokens configured, see `a2a help send` for auth flags.

## Learn more

<CardGroup cols={2}>
  <Card title="A2A" icon="network-wired" href="/features/a2a">
    Server and client feature docs
  </Card>

  <Card title="A2A Config" icon="arrow-right" href="/examples/a2a-config">
    Outbound client example
  </Card>
</CardGroup>