A2A (Agent2Agent protocol)
The missing inter-agent protocol in the wiki’s standards layer. The spoke already pages the context/skills standards — agentskills-spec (what an agent can do), agents-md (what it must know), and the cross-wiki MCP (how an agent reaches tools/data). A2A is the orthogonal axis: how agents talk to other agents. Originally built by Google, now donated to the Linux Foundation — the same open-standard-as-attractor pattern as agentskills-spec/agents-md.
What it standardizes
Agent-to-agent interoperability across vendors and frameworks — LangGraph, CrewAI, Semantic Kernel, ADK, and custom agents can collaborate without exposing internal memory, tools, or logic. Mechanisms:
- Agent Cards — a published capability-discovery descriptor (what an agent can do / how to reach it).
- Tasks — the unit of work exchanged and delegated between agents; streaming + async for long-running work (the same durability concern, at the protocol layer).
- Transport — JSON-RPC over HTTP.
A2A vs MCP — complementary, not competing
The cleanest framing this spoke has for its protocol layer:
- MCP = agent → tool. How one agent accesses tools/APIs/data.
- A2A = agent → agent. The “public internet” for agents to find and delegate to each other.
- MCP runs inside an A2A ecosystem — different layers. So the orchestrator → subagent fan-out pattern, so far an in-process harness concern, gets a cross-vendor wire format: orchestration can now span agents from different builders.
Why it matters here
- Fills the inter-agent gap beside skills/context/tool standards — the spoke’s “standards layer” was missing the agent↔agent edge. With A2A, the standardization-reach open question sharpens: skills (agentskills-spec), context (agents-md), tools (MCP), and now interop (A2A) are four distinct open standards, each a candidate attractor — or a new front for fragmentation (ACP and vendor-native schemes still coexist).
- Governance signal. Like agents-md (Linux Foundation) and agentskills-spec, a major vendor donating the spec to a neutral foundation is the recurring move to make a format an industry default rather than a house style.
Caveat
Spec/standard, not an outcome: adoption breadth is the open question (does A2A win the agent-interop layer or splinter against ACP / proprietary schemes?). Vendor-originated (Google), now foundation-governed.
Related
model-context-protocol · agentskills-spec · agents-md · agent-orchestration · adk · durable-agents · synthesis