A2A Protocol Specification

1. Protocol Overview

A2A Protocol is an open standard designed to enable seamless communication between autonomous AI agents. It provides a unified framework for agent discovery, capability negotiation, task execution, and result exchange.

Key Features

• Standardized message format across different agent implementations
• Flexible capability discovery and negotiation mechanism
• Secure and reliable communication channels
• Extensible architecture supporting various data types

2. Design Principles

Interoperability

Ensures agents from different vendors can communicate seamlessly

Scalability

Supports efficient communication in large-scale agent networks

Security

Built-in security mechanisms for authenticated communication

Extensibility

Flexible architecture allowing custom extensions and capabilities

3. Core Components

Agent Identity

Unique identification system for agents in the network

{
  "agent_id": "agent_12345",
  "name": "DataProcessor",
  "version": "1.0.0",
  "vendor": "AI Corp"
}

Message Structure

Standardized format for all agent communications

{
  "header": {
    "message_id": "msg_001",
    "timestamp": "2025-08-03T12:00:00Z",
    "sender": "agent_12345",
    "recipient": "agent_67890"
  },
  "payload": {
    "type": "task_request",
    "data": { /* task specific data */ }
  }
}

5. Detailed Message Format

Complete Message Schema

{
  "protocol_version": "1.0",
  "message_id": "unique_message_identifier",
  "timestamp": "ISO_8601_timestamp",
  "message_type": "REQUEST|RESPONSE|EVENT|HEARTBEAT",
  "priority": "URGENT|HIGH|NORMAL|LOW",
  "sender": {
    "agent_id": "sender_agent_identifier",
    "endpoint": "sender_communication_endpoint",
    "authentication": "authentication_token"
  },
  "recipient": {
    "agent_id": "recipient_agent_identifier",
    "endpoint": "recipient_communication_endpoint"
  },
  "payload": {
    "content_type": "application/json|text/plain|multipart/mixed",
    "encoding": "utf-8|base64",
    "compression": "none|gzip|lz4",
    "data": {
      "task_type": "specific_task_identifier",
      "parameters": {
        "input_data": "task_input_parameters",
        "constraints": "execution_constraints",
        "timeout": "maximum_execution_time"
      },
      "requirements": {
        "capabilities": ["required_agent_capabilities"],
        "resources": "required_computational_resources",
        "security_level": "required_security_clearance"
      }
    }
  },
  "metadata": {
    "correlation_id": "conversation_correlation_identifier",
    "conversation_context": "previous_message_references",
    "routing_info": "network_routing_information",
    "quality_of_service": "delivery_requirements"
  },
  "signature": "digital_signature_for_message_integrity"
}

6. Agent Card Specification

Agent Cards provide standardized capability descriptions, enabling efficient agent discovery and selection.

Agent Card Structure

{
  "agent_info": {
    "id": "unique_agent_identifier",
    "name": "human_readable_agent_name",
    "version": "semantic_version_string",
    "description": "detailed_agent_description",
    "vendor": "agent_developer_organization",
    "license": "usage_license_type"
  },
  "capabilities": {
    "services": [
      {
        "service_id": "data_processing",
        "name": "Data Processing Service",
        "description": "Advanced data transformation and analysis",
        "input_types": ["text", "json", "csv"],
        "output_types": ["json", "xml", "report"],
        "parameters": {
          "max_file_size": "100MB",
          "supported_formats": ["csv", "json", "xml"],
          "processing_time": "< 30 seconds"
        }
      }
    ],
    "supported_protocols": ["HTTP", "WebSocket", "gRPC"],
    "security_features": ["TLS", "OAuth2", "JWT"],
    "scalability": {
      "max_concurrent_requests": 100,
      "throughput": "1000 req/min",
      "availability": "99.9%"
    }
  },
  "technical_specs": {
    "runtime_environment": "Python 3.9+",
    "dependencies": ["numpy", "pandas", "requests"],
    "resource_requirements": {
      "cpu": "2 cores",
      "memory": "4GB",
      "storage": "10GB"
    }
  },
  "endpoint_info": {
    "primary_endpoint": "https://agent.example.com/api",
    "health_check": "https://agent.example.com/health",
    "documentation": "https://agent.example.com/docs"
  }
}

8. Communication Lifecycle

5-Step Communication Process

1

Discovery

Agent discovers available services through registry lookup

2

Handshake

Establish secure communication channel and verify capabilities

3

Negotiation

Negotiate task parameters and execution requirements

4

Execution

Execute requested task and monitor progress

5

Completion

Return results and close communication session

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