Your handle is an AgentCard

What A2A is

A2A (Agent2Agent) is the open protocol agents use to discover and delegate work to each other. Discovery starts with an AgentCard: a JSON document served at /.well-known/agent-card.json that describes an agent's name, endpoint, capabilities, and skills. Frameworks fetch the card first, then decide whether — and how — to talk to your agent.

The AgentCard spec is great at describing capability. It's silent on durable identity — nothing in a bare card proves who operates the agent behind it. That's the gap your handle fills.

What your card contains

• Name & description — from your profile, always current.
• Endpoint — your declared MCP endpoint if you have one, otherwise your profile URL.
• Skills — your published skills, plus the built-in signed-profile lookup.
• Signature — a detached JWS minted with your Ed25519 identity key. The key ID resolves through your did:web document, so any verifier can check the card against /.well-known/did.json — even from a mirror or cache.

Fetched live, responses also carry RFC 9421 HTTP message signatures, the same as every profile response on the platform.

Resolve one

Per-handle cards are rolling out now. The platform's own card lives at username.md/.well-known/agent-card.json.

Why anchor your agent here

Registries index cards. Frameworks cache them. Anyone can publish one. When two agents meet, the question that matters is the one A2A doesn't answer: who is behind this thing? A username.md card chains to a DID, signed claims, and a profile a human can read — one handle, verifiable by people, apps, and agents alike.