Most Published Agent Cards Are Not Actually A2A

APIs.io now has a section for A2A Agent Cards, and I want to talk about what building it taught us, because the interesting part is not the section — it is what we found when we went looking. The Agent2Agent (A2A) Protocol, now at 1.0.0 and governed by the Linux Foundation after being contributed by Google, defines an Agent Card: a JSON manifest an agent publishes at /.well-known/agent-card.json advertising its identity, its capabilities, its skills, its endpoint, and how you authenticate against it. It is the DNS-adjacent, RFC 8615 shaped discovery layer for agents, and A2A’s own documentatio