Agent-to-Agent (A2A) Optimization: Making Your Product Callable by AI Agents
A2A optimization makes your product discoverable and usable by autonomous AI agents via MCP, agent cards, and .well-known manifests. The 2026 playbook.
Definition
Agent-to-Agent (A2A) optimization is the practice of exposing your product so autonomous AI agents can discover it, understand its capabilities, and call it directly — through the Model Context Protocol (MCP), agent cards, and .well-known manifests — with no human in the loop.
The third audience
After humans and search crawlers, the third audience is agents that act. They don't read landing pages — they read manifests and call tools. If your product isn't machine-callable, it's invisible to them.
The A2A surface
An MCP server exposing typed tools over a stable endpoint
An agent card at /.well-known/agent.json (Google's Agent2Agent protocol) declaring skills and endpoints
A /.well-known/ai-plugin.json manifest for ChatGPT
An OpenAPI spec for the REST surface
Bearer auth an agent can set programmatically
Idempotency and clear, typed errors so retries are safe
Machine-readable errors; a token-efficient llms.txt
How Relm applies A2A
Relm ships a native MCP server at /mcp, an agent card plus plugin and MCP-discovery manifests under /.well-known/, an OpenAPI spec, bearer keys, and idempotency on every write — a reference implementation of an agent-callable product.
Frequently asked questions
What is the A2A protocol?
Google's Agent2Agent — an open protocol for agents to discover and delegate to each other via an "agent card" at /.well-known/agent.json.
What is MCP?
Model Context Protocol — the standard for giving an AI agent typed tools. Claude Code, Cursor, and ChatGPT speak it.
Do I need both MCP and an agent card?
They serve different discovery paths; publish both to maximize reach. MCP is how agents call you; the agent card is how they find and understand you.
Is A2A just an API?
An API is necessary but not sufficient — A2A adds machine discovery (manifests) and agent-friendly ergonomics (idempotency, typed tools, wieldable auth).