AgentGrade

A2A — Agent-to-Agent Protocol

Capability · Linux Foundation · Updated 2026-07-19

Status: v1.0.0 stable (March 2026), governed by the Linux Foundation; agent-card.json is IANA-registered · Authoritative source

The protocol for agents talking to agents: a site hosting an agent publishes a discoverable Agent Card declaring identity, skills, and endpoint, so other agents can find it, verify it, and delegate tasks to it.

The discovery surface is the Agent Card: a JSON manifest at /.well-known/agent-card.json — one of only two agent-era names actually registered in IANA’s well-known registry (August 2025, change-controlled by the Linux Foundation). Spec versions before v0.3.0 used agent.json; serve the new path and redirect the old one.

v1.0.0 (March 2026) is the project’s first stable, production-ready release, and its headline addition is signed Agent Cards: a signatures field lets a consuming agent verify cryptographically who published the card, closing the gap between “found a card” and “trust the card.” The Linux Foundation reported more than 150 organizations supporting the standard as of April 2026.

A minimal Agent Card

GET /.well-known/agent-card.json

{"name":"acme-support",
 "description":"Handles order and refund questions",
 "url":"https://agents.example.com/a2a",
 "version":"1.0.0",
 "skills":[{"id":"refund-status","description":"Check a refund"}]}

How AgentGrade checks it

The scanner probes the current agent-card path first and falls back to the legacy one, validating the card’s required fields — so a site is credited wherever it published, and hinted toward the registered path. Scan your site to see where you stand.

Related

All standards

RFC 9421 · Web Bot Auth · RFC 8615 · MCP · A2A · x402 · WebMCP · llms.txt · RFC 9309 · RFC 9110 · Index