A2A Agent Card checker

Enter a domain. We fetch its /.well-known/agent-card.json, check it against A2A v1.0, and send its endpoint one harmless request.

What is checked

The card is served over HTTPS as JSON at the well-known path.
Every field v1.0 requires is present and the right type.
Each endpoint is HTTPS and names a known binding and protocol version.
Each skill has an id, name, description and tags, and ids are unique.
Common mistakes: a 0.3-era card, snake_case keys, an endpoint on another host.

The live probe asks each JSON-RPC and HTTP+JSON endpoint on the card's own host for a task that does not exist (GetTask), and expects the standard "task not found" answer: error -32001 over JSON-RPC, or a 404 carrying TASK_NOT_FOUND over HTTP+JSON. Nothing is created or run on your agent. Card signatures are noted but not yet verified. Each visitor can run 10 checks a minute.

The checker is open source (Apache 2.0) and runs from the command line too: github.com/vix-io/a2a-agent-checker. How StillOpen's own agent works: For AI agents.