a2a-dev-patterns

A2A Development Patterns

Before writing code

Fetch live docs:

1. Fetch https://a2a-protocol.org/latest/specification/ for the latest protocol details
2. Web-search a2a protocol best practices multi-agent architecture for community patterns
3. Web-search site:github.com a2aproject A2A samples patterns for reference architectures
4. Web-search multi-agent system design patterns for general multi-agent architecture guidance

Conceptual Architecture

Orchestration Topologies

Hub-and-Spoke (Orchestrator)

A central coordinator agent delegates subtasks to specialist agents:

                    ┌→ Research Agent
Coordinator Agent ──┼→ Analysis Agent
                    └→ Writing Agent

• Pros: Centralized control, clear task routing, easy to monitor
• Cons: Single point of failure, coordinator bottleneck
• Use when: Well-defined subtask decomposition, need for aggregation

Peer-to-Peer (Mesh)

Agents discover and communicate directly with each other:

Agent A ←→ Agent B
  ↕           ↕
Agent C ←→ Agent D

• Pros: No single point of failure, flexible
• Cons: Complex routing, harder to monitor, potential loops
• Use when: Agents are loosely coupled, dynamic discovery needed

Pipeline (Chain)

Tasks flow through a sequence of agents:

Input → Agent A → Agent B → Agent C → Output

• Pros: Simple flow, easy to reason about, composable
• Cons: Sequential latency, failure in one stage blocks all
• Use when: Clear transformation stages, ETL-like workflows

Hierarchical (Tree)

Manager agents delegate to team agents, which may further delegate:

CEO Agent
├── Marketing Manager Agent
│   ├── Content Agent
│   └── SEO Agent
└── Engineering Manager Agent
    ├── Frontend Agent
    └── Backend Agent

• Pros: Natural decomposition, scoped authority, scalable
• Cons: Deep hierarchies add latency, complex coordination
• Use when: Large organizations of agents, domain separation