Ecosystem

A2E, MCP & A2A

How A2E fits in the agentic AI ecosystem.

The Three Protocols

The agentic AI ecosystem is built on three complementary protocols, each solving a different problem:

┌─────────────────────────────────────────────────────┐
│                   DISCOVERY LAYER                    │
│  ┌───────────────────────────────────────────────┐  │
│  │  A2E: "Which MCP serves this entity?"         │  │
│  │  (Real-world entity → MCP endpoint)           │  │
│  └───────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────┘
                          │
                          ▼
┌─────────────────────────────────────────────────────┐
│                 INTERACTION LAYER                    │
│  ┌─────────────────────┐ ┌─────────────────────┐   │
│  │ MCP                 │ │ A2A                 │   │
│  │ Agent ↔ Tool        │ │ Agent ↔ Agent       │   │
│  │ (use capabilities)  │ │ (collaborate)       │   │
│  └─────────────────────┘ └─────────────────────┘   │
└─────────────────────────────────────────────────────┘

What Each Protocol Does

Protocol	Question it answers	Interaction type
MCP	"What can this server do?"	Agent → Tool (stateless)
A2A	"How do I collaborate with this agent?"	Agent ↔ Agent (stateful, peer)
A2E	"Which MCP serves this real-world entity?"	Discovery (before interaction)

The Missing Link

MCP directories tell you what servers exist and their capabilities. But when a user says "Book a table at Acme Restaurant", the agent needs to know which MCP serves Acme Restaurant specifically.

Without A2E:
  User: "Book at Acme Restaurant"
  Agent: "I know 50 booking MCPs... but which one has Acme?" ❌

With A2E:
  User: "Book at Acme Restaurant"
  Agent: GET acme-restaurant.com/.well-known/entity-card.json
       → mcp.booking-provider.com
       → Execute reservation ✓

A2E bridges the gap between real-world entities (businesses, services, places) and the agentic infrastructure (MCPs, agents).

How They Work Together

A complete agentic flow might use all three protocols:

1. DISCOVERY (A2E)
   "Book a haircut at Le C Coiffeur"
   → GET le-c-coiffeur.com/.well-known/entity-card.json
   → MCP endpoint: mcp.planity.com

2. INTERACTION (MCP)
   → Connect to mcp.planity.com
   → Call: get_availability(entity_ref: "le-c-coiffeur")
   → Call: create_booking(...)

3. COLLABORATION (A2A) - if needed
   → Payment agent handles transaction
   → Calendar agent syncs appointment

Comparison Table

Aspect	A2E	MCP	A2A
Purpose	Entity discovery	Tool usage	Agent collaboration
Published by	Entity (business)	Tool provider	Agent provider
Discovery	`/.well-known/entity-card.json`	Registry / direct	Agent cards
Identity	Domain-based	Endpoint-based	Agent card
Stateful	No	No	Yes

Fully Complementary

A2E does not compete with MCP or A2A. It operates at a different layer:

MCP defines how to interact with a server once you know its endpoint
A2A defines how agents collaborate on complex tasks
A2E helps you find the right endpoint for a specific entity

Think of A2E as DNS for the agentic world: it resolves real-world names to technical endpoints.