A2A Client

Connect to remote A2A agents — use them as tools, team members, or call them directly.

A2A Client

A2ARemoteAgent lets you connect to any A2A-compliant agent and use it as if it were a local RadarOS agent. It supports discovery, synchronous calls, streaming, and can be used as a tool or team member.

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Discovery

First, discover the remote agent by fetching its Agent Card:

import { A2ARemoteAgent } from "@radaros/core";

const remote = new A2ARemoteAgent({
  url: "http://remote-service:3001",
});

const card = await remote.discover();

console.log(card.name);           // "RadarOS Agent Server"
console.log(card.skills);         // [{ id: "assistant", ... }]
console.log(card.capabilities);   // { streaming: true, ... }

---

Direct Calls

Synchronous (message/send)

const result = await remote.run("What is the capital of France?");
console.log(result.text);  // "Paris"

Streaming (message/stream)

for await (const chunk of remote.stream("Tell me a story")) {
  if (chunk.type === "text") {
    process.stdout.write(chunk.text);
  }
}

---

As a Tool

Wrap the remote agent as a ToolDef so an orchestrator agent can call it:

import { Agent, openai } from "@radaros/core";

const remote = new A2ARemoteAgent({
  url: "http://calculator-service:3001",
});
await remote.discover();

const orchestrator = new Agent({
  name: "orchestrator",
  model: openai("gpt-4o"),
  instructions: "Delegate math tasks to the remote calculator.",
  tools: [remote.asTool()],
});

const result = await orchestrator.run("What is 2^10?");
console.log(result.text);  // "1024"

The tool is automatically named a2a_{agentName} and uses the agent’s description from the Agent Card.

---

As a Team Member

Remote A2A agents can participate in RadarOS Teams alongside local agents:

import { Agent, openai, A2ARemoteAgent, Team, TeamMode } from "@radaros/core";

const localWriter = new Agent({
  name: "writer",
  model: openai("gpt-4o-mini"),
  instructions: "You are a creative writer.",
});

const remoteResearcher = new A2ARemoteAgent({
  url: "http://research-service:3001",
});
await remoteResearcher.discover();

const team = new Team({
  name: "content-team",
  mode: TeamMode.Coordinate,
  model: openai("gpt-4o"),
  members: [localWriter, remoteResearcher],
  instructions: "Use the writer for creative tasks, the researcher for facts.",
});

const result = await team.run("Write a blog post about quantum computing");

---

Authentication

Pass custom headers for authenticated A2A servers:

const remote = new A2ARemoteAgent({
  url: "https://secure-agent.example.com",
  headers: {
    Authorization: "Bearer my-api-token",
  },
});

---

Configuration

url · string · required

Base URL of the remote A2A agent (e.g. "http://localhost:3001").

headers · Record<string, string>

Custom headers sent with every request (useful for authentication).

name · string

Override the agent name (otherwise discovered from the Agent Card).

timeoutMs · number · default: "60000"

Request timeout in milliseconds.

---

API

Method	Returns	Description
discover()	A2AAgentCard	Fetch the Agent Card and populate metadata.
run(input, opts?)	RunOutput	Send message/send and return the result.
stream(input, opts?)	AsyncGenerator<StreamChunk>	Send message/stream and yield chunks.
asTool()	ToolDef	Wrap as a tool for use by other agents.
getAgentCard()	A2AAgentCard | null	Return the cached Agent Card.