Guide

External Agents 101

How your agents talk to agents from other systems. LangChain, CrewAI, AutoGPT, or any A2A-compliant agent — without those systems needing to know anything about Cadreen.

What is A2A?

A2A is how agents from different systems find each other, talk to each other, and work together — without sharing their secrets. Think of it like email. Gmail can talk to Outlook can talk to Yahoo. They don't need to be built by the same company.

Your support agent (built on Cadreen) can ask a billing agent (built on LangChain) to check a customer's refund status. Your research agent (built on CrewAI) can hand off a document analysis task to a Cadreen agent that has the right tools.

How it works

Four steps. Click each one to learn more.

A2A vs Federation

Three ways agents communicate. Same workspace: automatic, nothing to set up. Federation: different workspaces within Cadreen. A2A: agents on entirely different platforms.

Aspect	Federation	External (A2A)
Who talks to whom	Cadreen agent to Cadreen agent	Cadreen agent to any agent
Organization	Same organization, different workspaces	Different organizations, different systems
Authentication	Workspace-level trust	API key per agent
Governance	Shared policies	Your policies apply to all interactions
Knowledge sharing	Explicit, per-field control	Skills only — no memory, no tools
Use case	Internal teams collaborating	External partners, multi-vendor systems

Note

Federation connects different workspaces within Cadreen. A2A connects to agents on external platforms. Agents in the same workspace communicate by default — no setup needed. You can use all three from a single workspace.

Security

Four layers protect every cross-platform interaction.

Authentication

API key required. Every request is authenticated.

Governance

Every interaction goes through your rules. No exceptions.

Consent

You approve every external connection before it's active.

Audit

Every cross-platform interaction is logged.

Task lifecycle

External tasks go through states. Click each state to learn more.

A2A vs MCP

They complement each other. MCP is how an agent connects to its tools. A2A is how agents collaborate.

MCP — agent to tool

Your agent connects to GitHub, Stripe, and Slack. Tools.

A2A — agent to agent

Your agent delegates a billing task to another agent. Collaboration.

Note

Cadreen already supports MCP. Adding A2A completes the picture.

Quick start with SDK

Connect an external agent using the Cadreen SDK. The dashboard also supports this via the External tab.

Python

TEXT

from cadreen import Cadreen

client = Cadreen(api_key="sk_cadreen_...")

# Connect an external agent
connection = client.external_agents.connect(
    agent_id="your-agent-id",
    agent_card_url="https://external.example.com/.well-known/agent.json"
)

# Approve the connection
client.external_agents.approve(
    agent_id="your-agent-id",
    connection_id=connection.id
)

Go

TEXT

package main

import (
    "context"
    "github.com/timothy-billingrails/cadreen-sdks/go/cadreen"
)

func main() {
    client := cadreen.NewClient("sk_cadreen_...")

    // Connect an external agent
    conn, _ := client.ConnectExternalAgent(context.Background(),
        "your-agent-id",
        cadreen.ConnectExternalAgentRequest{
            AgentCardURL: "https://external.example.com/.well-known/agent.json",
        },
    )

    // Approve the connection
    client.ApproveExternalConnection(context.Background(),
        "your-agent-id",
        conn.ID,
    )
}

Note

The external agent must publish an Agent Card at /.well-known/agent.json. Cadreen fetches this to discover the agent's capabilities.

Next steps

External Agents Cookbook — Connect your first external agent
Agent Dashboard — Manage agents and their external connections
Settings — Enable external agent connections