The Agent Protocol originated as a community-driven open standard defining a unified HTTP API interface for communicating with AI agents. Initially developed by the AI Engineer Foundation, the concept of standardizing agent-to-agent communication evolved significantly.¹⁾ By mid-2025, Google launched the Agent2Agent (A2A) Protocol under the Linux Foundation's governance, which has become the primary open standard for secure, interoperable communication between AI agents across platforms and vendors.²⁾

The original Agent Protocol specification defined common REST API endpoints for interacting with any AI agent:

• POST /ap/v1/agent/tasks - Create a new task
• GET /ap/v1/agent/tasks/{id} - Retrieve task status
• POST /ap/v1/agent/tasks/{id}/steps - Execute the next step
• GET /ap/v1/agent/tasks/{id}/artifacts - List task artifacts

This standardization enabled framework-agnostic agent interaction. Frameworks like AutoGPT and BabyAGI adopted it to ensure agents built on different stacks could communicate through a common interface. The specification used JSON payloads over HTTP with clear lifecycle management for tasks and steps.

The A2A Protocol, launched in June 2025 by Google and governed by the Linux Foundation, extends the vision of agent interoperability to enterprise scale:

• GitHub: github.com/a2aproject/A2A
• Standards: Built on HTTP, SSE (Server-Sent Events), and JSON-RPC
• Governance: Linux Foundation with vendor-neutral oversight

• Agent Discovery: Agents can find and identify each other's capabilities dynamically
• Secure Messaging: Enterprise-grade authentication with OpenAPI parity, authorization controls
• Task Coordination: Support for long-running tasks with real-time feedback, notifications, and state updates
• Human-in-the-Loop: Built-in support for processes requiring human approval, lasting hours or days

Over 100 technology companies are involved, including:

• Google Cloud - Core developer
• Microsoft (Azure AI Foundry) - Includes A2A alongside Semantic Kernel and AutoGen
• Salesforce (Agentforce) - Cross-platform orchestration
• AWS, Cisco (Outshift/AGNTCY), SAP, ServiceNow

A2A and MCP are complementary standards:

• MCP standardizes how agents connect to tools and data sources (agent-to-tool)
• A2A standardizes how agents communicate with each other (agent-to-agent)

Together they form the emerging interoperability stack for agentic AI systems. Bain's 2025 analysis projects 5-10% of enterprise tech spending directed toward agent platforms using these standards over the next 3-5 years.

• Agent Network Protocol
• A2A vs MCP vs AG-UI
• AG-UI Protocol
• Agent Communication Protocol
• Agent Interface Design