A2A Protocol
If MCP lets a customer's AI talk to your tools, A2A lets a customer's AI talk to your AI. That's where the conversational economy starts.
Strong signal and real results. Worth committing a pilot to.
Agent protocol·Open-source
What It Is
Agent2Agent (A2A) Protocol is an open specification for inter-agent communication. It defines how an AI agent can discover, authenticate with, and delegate tasks to another AI agent, including specialist agents representing specific businesses, services, or expert domains. Originally developed by Google and donated to the Linux Foundation, A2A v1.0 launched in early 2026 with Signed Agent Cards (cryptographic verification of agent provenance), multi-tenancy (one endpoint serves many agents), multi-protocol bindings (JSON-RPC and gRPC), and version negotiation.
Why It Matters
For AEO, A2A is the protocol for the next layer of business representation. A customer's AI assistant doesn't just retrieve facts about your business or call a tool you exposed. It converses with your business's agent, which can negotiate quotes, run complex eligibility checks, hand off to humans, or follow proprietary processes. Businesses that publish well-defined A2A agents become first-class participants in agent-mediated commerce. Businesses that don't are limited to whatever generic answer engines can synthesise about them.
Production deployments are already live at Microsoft, AWS, Salesforce, SAP, and ServiceNow. 150+ organisations now back the protocol. The trust model (Signed Agent Cards) is the part most relevant to AEO buyers because it solves who-is-this-really verification, which is what consumer-facing AI assistants need before delegating real actions.
Key Developments
- Early 2026: A2A v1.0 released with Signed Agent Cards, multi-tenancy, multi-protocol bindings (JSON-RPC and gRPC), and version negotiation.
- 2025: A2A spec donated to the Linux Foundation. Production deployments at Microsoft, AWS, Salesforce, SAP, and ServiceNow announced.
- 2025: Initial drafts circulated and reference implementations emerged.
What to Watch
Watch how A2A and MCP interoperate. Most agent stacks will need both. Track which AEO platforms add A2A agent publishing as a feature alongside traditional content optimisation. Watch the trust and reputation layer. Signed Agent Cards solve provenance verification, but rating and trust systems for what an agent can be relied on to do are still immature.
Strengths
- Peer-to-peer model: Treats business agents as first-class participants, not just tools. Enables negotiation, clarification, and complex flows.
- Linux Foundation governance: Vendor-neutral with strong governance. Reduces single-vendor risk.
- Production traction: Live deployments at Microsoft, AWS, Salesforce, SAP, and ServiceNow. 150+ organisations involved.
- Complements MCP: Different abstraction layer. A2A doesn't replace MCP, it sits above it.
Considerations
- Earlier than MCP in consumer reach: Adoption among consumer-facing AI assistants is still patchy. Most production deployments today are enterprise-to-enterprise.
- Reputation gap: Signed Agent Cards verify origin, but rating and reputation systems for published agents are immature.
- Discoverability: Like MCP, no consumer-grade agent directory yet. Businesses need to be referenced or registered to be reached.
- Investment vs payoff: Building a proper A2A agent is non-trivial. Near-term ROI vs traditional AEO is unclear for most businesses.
A2A Protocol· ACP — Agent Communication Protocol· Computer Use· Model Context Protocol· Agent discovery manifests· OAGP — Open Agent Gateway Protocol