A2A vs MCP: Tools or Agents? The difference that will change how we build AI systems : AntonioCortes.com

Two protocols, two philosophies

In recent months, two protocols have emerged that will change how we build AI systems: Agent2Agent Protocol (A2A) from Google and Model Context Protocol (MCP) from Anthropic. But here’s the thing: they don’t compete with each other.

In fact, after analyzing both for weeks, I’ve realized that understanding the difference between A2A and MCP is crucial for anyone building AI systems beyond simple chatbots.

The key lies in one question: Are you connecting an AI with tools, or are you coordinating multiple intelligences?

The fundamental difference: Tools vs Agents

MCP: “Lend me your hammer”

Model Context Protocol is fundamentally about tool access. It allows an AI model to use external resources in a standardized way: APIs, databases, file systems, web services.

// MCP in action
const mcpClient = new MCPClient();
await mcpClient.callTool('database', 'query', {
  sql: 'SELECT * FROM users WHERE active = true',
  timeout: 5000
});

📚 Complete MCP specification

A2A: “Let’s work together”

Agent2Agent Protocol is about agent collaboration. It defines how multiple AI systems can discover each other, communicate, and coordinate work together to solve complex tasks.

// A2A in action
const agent = new A2AAgent('data-analyst');
const response = await agent.collaborate({
  task: "analyze Q2 sales patterns",
  with: ["market-research-agent", "forecast-agent"],
  mode: "conversational"
});

📚 A2A Protocol documentation

A metaphor that clarifies it

Imagine an autonomous car repair shop:

MCP is the shop organization:

“The wrench is in drawer 3”
“To lift the car, use command lift_car(height: 2m)”
“Manuals are in the documentation system”

A2A is the communication between mechanics:

“There’s an oil leak, can you check the engine while I check the brakes?”
“I need this model’s history, do you have access to the database agent?”
“The customer is asking about repair time, how much do you have left?”

Technical comparison that matters

Aspect	MCP	A2A
Purpose	Model → Tool	Agent ↔ Agent
Communication	Structured calls	Conversational
Duration	Request/Response	Long sessions
Complexity	Low (known APIs)	High (dynamic coordination)
State	Stateless	Stateful
Use cases	Data access, automation	Complex collaboration, multi-step resolution

Where to use each (real cases)

MCP shines for:

1. Integrating AI with existing systems

# MCP server for your CRM
npx @company/mcp-crm-server --config production

Claude Desktop can now access customer data, create tickets, update records.

🔧 Official MCP servers | MCP for GitHub

2. Automating defined tasks

Process invoices → extract data → update accounting
Analyze logs → detect errors → create support tickets
Review code → run tests → generate reports

3. Controlled resource access

# MCP configuration for development team
mcp_servers:
  - name: github
    permissions: [read_repos, create_issues]
  - name: database
    permissions: [read_only]
  - name: monitoring
    permissions: [read_metrics]

A2A ideal for:

1. Tasks requiring multiple specialties

// Complex market analysis
const marketAnalysis = await coordinator.orchestrate({
  agents: [
    'financial-analyst',    // Numbers and trends
    'social-sentiment',     // Social media analysis
    'competitive-intel',    // Competition analysis
    'economic-forecaster'   // Macroeconomic predictions
  ],
  task: "evaluate viability of expansion to Asian market"
});

🔧 Python A2A implementation | A2A examples

2. Complex problem solving

Distributed debugging where each agent analyzes a component
Scientific research with specialists in different areas
Strategic business planning

3. Adaptive systems Agents that can discover new services, adapt to environment changes, form dynamic teams as needed.

Why they don’t compete: They complement each other

In real systems, you need both:

// An A2A agent that uses MCP tools
class DataAnalysisAgent extends A2AAgent {

  async analyzeUserBehavior(request) {
    // Use MCP to access data
    const userData = await this.mcpClient.callTool('analytics-db', 'query', {
      timeframe: request.period,
      metrics: ['sessions', 'conversion', 'retention']
    });

    // Use A2A to collaborate with other agents
    const insights = await this.collaborate({
      with: ['ml-insights-agent', 'business-context-agent'],
      data: userData,
      task: 'generate_actionable_insights'
    });

    return insights;
  }
}

The challenges ahead

MCP: Operational maturity

Permission management at enterprise scale
Monitoring and debugging of complex integrations
Versioning and backwards compatibility

A2A: Distributed coordination

State consistency between agents
Handling partial failures in collaborations
Security in communications between untrusted agents

My experience implementing both

I’ve been experimenting with both protocols in real projects. What I’ve learned:

MCP is production-ready today

Integration with existing systems is straightforward. In a week we had Claude Desktop accessing our GitLab, metrics database, and documentation system.

# Setup that worked from day one
docker-compose up mcp-gitlab mcp-postgres mcp-docs

🚀 MCP Quickstart | MCP Inspector for debugging

A2A needs more maturity

The concepts are solid, but the current implementation requires a lot of boilerplate code. Coordination between agents is complex to debug.

But the potential is enormous. I see teams using A2A for cases that previously required weeks of manual coordination.

📖 Complete A2A guide

Practical recommendations

Start with MCP if…

You have existing systems that need AI integration
You want to automate well-defined tasks
You need quick results with minimal investment

Experiment with A2A if…

You work on complex problems requiring multiple specialties
You have time to experiment with emerging technology
Your use case can’t be solved with simple tool access

Combine both when…

You’re building advanced AI systems for production
Each agent needs access to specific resources (MCP) but also collaboration (A2A)
You want maximum flexibility

The future: Distributed AI

These protocols point to where we’re going: distributed AI systems where multiple specialized agents collaborate, each with access to the tools they need.

It’s not science fiction. It’s already happening:

Walmart is experimenting with collaborative agents for logistics
Google uses A2A internally for research assistants
Anthropic uses MCP to connect Claude with internal infrastructure

Conclusion: The right question

The question is not “A2A vs MCP?” but “What kind of intelligence am I building?”

An AI that needs tool access? → MCP
Multiple AIs that need to collaborate? → A2A
A complete intelligent system? → Both

We’re at a unique moment where we can choose how to structure the AI systems of the future. The right decision today will determine how flexible and powerful our systems will be tomorrow.

Resources to get started

Model Context Protocol (MCP)

Agent2Agent Protocol (A2A)

Tools and community

🔍 MCP Inspector - MCP connection debugging
💬 MCP Discord
🐙 Awesome MCP - Curated resource list
📹 Tutorial videos

What do you think? Have you experimented with any of these protocols? Do you see use cases where both are necessary?

My next experiment: A code analysis system where specialized agents (security, performance, architecture) collaborate via A2A, but each accesses specific tools (Git, IDEs, knowledge bases) via MCP.

If you’re experimenting with this, I’d love to know your use cases and lessons learned.