A2A JSON-RPC reference

The A2A JSON-RPC 2.0 methods Oxagen implements, with example request/response exchanges.

All A2A methods are JSON-RPC 2.0 calls to a single endpoint:

POST https://api.oxagen.sh/a2a
Content-Type: application/json
Authorization: Bearer ox_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Methods

Method	Purpose	Response
`message/send`	Send a message, run the task to completion	`Task`
`message/stream`	Send a message, stream progress	SSE of `Task` / status-update / artifact-update
`tasks/get`	Fetch a task's current state	`Task`
`tasks/cancel`	Cancel a non-terminal task	`Task`
`tasks/resubscribe`	Re-attach an SSE stream to a task	SSE status-update
`agent/getAuthenticatedExtendedCard`	Fetch the authenticated Agent Card	`AgentCard`

Push-notification config methods (tasks/pushNotificationConfig/*) are advertised as unsupported (capabilities.pushNotifications: false) and return error -32003.

message/send

Request

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "message/send",
  "params": {
    "message": {
      "role": "user",
      "parts": [{ "kind": "text", "text": "Summarize the Acme account." }],
      "messageId": "c1a4d2e0-0000-4000-8000-000000000001"
    }
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "kind": "task",
    "id": "a2a_7h3k9m2p5q8r1t4v6x9z2b",
    "contextId": "ctx_9f8e7d6c5b4a39281706f5e4d3c2b1a0",
    "status": {
      "state": "completed",
      "timestamp": "2026-07-04T12:00:03.412Z"
    },
    "artifacts": [
      {
        "artifactId": "b7c1…",
        "name": "response",
        "parts": [{ "kind": "text", "text": "Acme is a mid-market…" }]
      }
    ],
    "history": [
      { "kind": "message", "role": "user", "parts": [{ "kind": "text", "text": "Summarize the Acme account." }], "messageId": "c1a4…" },
      { "kind": "message", "role": "agent", "parts": [{ "kind": "text", "text": "Acme is a mid-market…" }], "messageId": "…" }
    ]
  }
}

The returned id is the durable task id (poll it with tasks/get). Pass the returned contextId back in a later message/send to continue the same conversation.

Same params as message/send. The response is text/event-stream; each SSE data: line is a JSON-RPC response envelope wrapping one event. The first event is the initial Task (state submitted), followed by status updates, incremental artifact chunks, and a final status update with final: true.

data: {"jsonrpc":"2.0","id":1,"result":{"kind":"task","id":"a2a_…","contextId":"ctx_…","status":{"state":"submitted"}}}

data: {"jsonrpc":"2.0","id":1,"result":{"kind":"status-update","taskId":"a2a_…","contextId":"ctx_…","status":{"state":"working"},"final":false}}

data: {"jsonrpc":"2.0","id":1,"result":{"kind":"artifact-update","taskId":"a2a_…","contextId":"ctx_…","artifact":{"artifactId":"b7c1…","name":"response","parts":[{"kind":"text","text":"Acme is"}]},"append":true,"lastChunk":false}}

data: {"jsonrpc":"2.0","id":1,"result":{"kind":"status-update","taskId":"a2a_…","contextId":"ctx_…","status":{"state":"completed"},"final":true}}

The stream closes when a status-update with final: true is sent (the task reached a terminal state).

tasks/get

{ "jsonrpc": "2.0", "id": 2, "method": "tasks/get",
  "params": { "id": "a2a_7h3k9m2p5q8r1t4v6x9z2b", "historyLength": 10 } }

Returns the Task. historyLength optionally clamps the returned message history. Unknown ids return error -32001 (Task not found).

tasks/cancel

{ "jsonrpc": "2.0", "id": 3, "method": "tasks/cancel",
  "params": { "id": "a2a_7h3k9m2p5q8r1t4v6x9z2b" } }

Cancels a non-terminal task and returns the updated Task (state canceled). A task that already reached a terminal state returns error -32002 (Task not cancelable).

Task states

submitted · working · input-required · auth-required · completed · canceled · failed · rejected · unknown

Terminal states (completed, canceled, failed, rejected) are immutable.

Error codes

Code	Meaning
`-32700`	Parse error (invalid JSON)
`-32600`	Invalid request
`-32601`	Method not found
`-32602`	Invalid params
`-32603`	Internal error
`-32001`	Task not found
`-32002`	Task not cancelable
`-32003`	Push notifications not supported