Protocol support

For people building workers: what the mod needs from your Agent Card and endpoint. In short: A2A 1.0 or 0.3, the JSON-RPC binding, a send that returns immediately, and GetTask for polling. Write a worker has a working example.

VersionsCopy Anchor Link

The mod speaks A2A 1.0 and 0.3 over JSON-RPC. It reads the version from the worker's Agent Card, and it is tested end to end against @a2a-js/sdk 1.3.0.

To pick an endpoint, it looks at the card's supportedInterfaces for a JSON-RPC entry with protocol version 1.x, then 0.3. If there is none, it falls back to the 0.3 card fields: url, or the JSON-RPC entry in additionalInterfaces.

A card with no JSON-RPC endpoint is rejected when you add the worker.

MethodsCopy Anchor Link

The mod sends the A2A-Version: 1.0 header to 1.0 workers, and when it fetches a card. A 1.0 server that also serves 0.3 would otherwise answer with the 0.3 card.

A message asks the worker to return without waiting for the task to finish. In 1.0 that is returnImmediately; in 0.3 it is blocking: false.

Cards and resultsCopy Anchor Link

• The card is fetched from /.well-known/agent-card.json, or from the URL you gave if it ends in .json.
• A card that lists securityRequirements (1.0) or security (0.3) marks the worker as needing a token.
• A task is live in the submitted and working states. The mod also recognises completed, failed, canceled, rejected, input-required and auth-required.
• A result is the task's status message followed by its artifacts, as text. Data parts show as JSON. File parts show their name, type and address; inline file bytes are not shown.

What it doesn't do (yet)Copy Anchor Link

• Streaming. The mod runtime returns a whole response body at once, so there is no SSE.
• Push notifications.
• Inbound or server mode. The mod is a client only.
• The gRPC and REST bindings. JSON-RPC only.
• OAuth flows. Workers get a bearer token.