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Guillaume Laforge
be20e09b1d
* doc: A2A support in ADK Java * doc: fix spelling for the Agent2Agent protocol name * doc: addressing Kris' comments on the A2A Java documentation
87 lines
4.0 KiB
Markdown
87 lines
4.0 KiB
Markdown
# Quickstart: Exposing a remote agent via A2A
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<div class="language-support-tag">
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<span class="lst-supported">Supported in ADK</span><span class="lst-java">Java</span><span class="lst-preview">Experimental</span>
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</div>
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This quickstart covers the most common starting point for any developer: **"I have an agent. How do I expose it so that other agents can use my agent via A2A?"**. This is crucial for building complex multi-agent systems where different agents need to collaborate and interact.
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## Overview
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This sample demonstrates how you can expose an ADK agent using Quarkus so that it can be then consumed by another agent using the A2A Protocol.
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In Java, you build an A2A server natively by relying on the ADK A2A extension. This uses the Quarkus framework, meaning you just configure your agent directly within your standard Quarkus `@ApplicationScoped` bindings.
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```text
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┌─────────────────┐ ┌───────────────────────────────┐
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│ Root Agent │ A2A Protocol │ A2A-Exposed Check Prime Agent │
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│ │────────────────────────────▶│ (localhost:9090) │
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└─────────────────┘ └───────────────────────────────┘
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```
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## Exposing the Remote Agent with Quarkus
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Using Quarkus, you map your agent into an A2A execution endpoint without manually wrangling incoming HTTP JSON-RPC payloads or sessions.
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### 1. Getting the Sample Code { #getting-the-sample-code }
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The fastest way to get started is by checking the standalone Quarkus app inside the `contrib/samples/a2a_server` folder within the [**`adk-java`** repo](https://github.com/google/adk-java).
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```bash
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cd contrib/samples/a2a_server
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```
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### 2. How it works
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The core runtime uses a provided `AgentExecutor` which requires you to build a CDI `@Produces` bean configuring your native `BaseAgent`. The Quarkus A2A extension discovers this and wires the endpoints automatically.
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```java title="A2aExposingSnippet.java"
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--8<-- "examples/java/snippets/src/main/java/a2a/A2aExposingSnippet.java:a2a-launcher"
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```
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The app handles incoming JSON-RPC calls over HTTP mounted on `/a2a/remote/v1/message:send` automatically forwarding parts, history, and contexts directly into your `BaseAgent` flow.
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### 3. Start the Remote A2A Agent server { #start-the-remote-a2a-agent-server }
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Within the native ADK structure, you can run the Quarkus dev mode task:
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```bash
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./mvnw -f contrib/samples/a2a_server/pom.xml quarkus:dev
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```
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Once executed, Quarkus automatically hosts your A2A compliant REST paths. A manual `curl` allows you to immediately smoke test the payload using native A2A specifications:
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```bash
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curl -X POST http://localhost:9090 \
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-H "Content-Type: application/json" \
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-d '{
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"jsonrpc": "2.0",
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"id": "cli-check",
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"method": "message/send",
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"params": {
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"message": {
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"kind": "message",
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"contextId": "cli-demo-context",
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"messageId": "cli-check-id",
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"role": "user",
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"parts": [
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{ "kind": "text", "text": "Is 3 prime?" }
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]
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}
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}
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}'
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```
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### 4. Check that your remote agent is running { #check-that-your-remote-agent-is-running }
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A proper agent card is exposed over a standard path representing your instance automatically:
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[http://localhost:9090/.well-known/agent-card.json](http://localhost:9090/.well-known/agent-card.json)
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You should be able to see the name dynamically mirrored from your agent configuration inside the response JSON.
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## Next Steps
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Now that you have exposed your agent via A2A, the next step is to learn how to consume it from another agent orchestrator natively.
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- [**A2A Quickstart (Consuming) for Java**](./quickstart-consuming-java.md): Learn how your agent orchestrator wrapper connects downstream to exposed services.
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