A2A Well-Known Agent Card Discovery

The path

https://{domain}/.well-known/agent.json. Reserved by RFC 8615. Always over HTTPS.

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Content

GET https://weather.example.com/.well-known/agent.json HTTP/1.1

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: max-age=300

{
  "name": "Weather Agent",
  "description": "...",
  "url": "https://weather.example.com/a2a",
  "version": "1.2.0",
  "capabilities": {...},
  "skills": [...]
}

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Caching

Server should set Cache-Control: max-age=300. Cards are stable but not immutable — 5 min TTL balances freshness + load.