Task and Response

Every message/send produces a Task. All three Caoliao skills are synchronous queries, so by the time the request returns the Task has finished and the result is in the same response.

Lifecycle

submitted → working → (artifact-update) → completed
                                       └→ failed

Since the service does not stream, you never observe the intermediate states — the response you receive already carries completed or failed in status.state.

Successful response

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "kind": "task",
    "id": "9332c282-1fa7-4c42-96ac-58e4e2f88f4c",
    "contextId": "e9c10667-e79b-4c99-b05f-0cb237067127",
    "status": {
      "state": "completed",
      "timestamp": "2026-08-12T17:14:13.272Z"
    },
    "history": [
      {
        "kind": "message",
        "role": "user",
        "messageId": "m1",
        "parts": [{ "kind": "text", "text": "What is this QR code? https://qr71.cn/okDISU/qssTnoy" }]
      }
    ],
    "artifacts": [
      {
        "artifactId": "6915a6bd-d63c-42e6-b629-8aed3bb06236",
        "name": "entity",
        "parts": [
          { "kind": "data", "data": { "...": "ObjectCard v2" } },
          { "kind": "text", "text": "..." }
        ]
      }
    ]
  }
}

Field	Description
id	Task id, used for tasks/get
contextId	Conversation context id, shared by Tasks in the same exchange
status.state	completed or failed
history	Messages exchanged in this interaction
artifacts	The result. Caoliao returns exactly one

The two artifact parts

Every artifact contains two parts:

• DataPart (kind: "data") — structured output for programs. The shape depends on the skill, see Skills
• TextPart (kind: "text") — a one-line summary you can put straight into a conversation without summarizing again

The artifact's name tells you what came back: entity, records or actions.

Note: summary text is written in Chinese.

Looking up a finished Task

curl -X POST https://a2a.objqr.com/a2a/jsonrpc \
  -H 'content-type: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "id": "2",
    "method": "tasks/get",
    "params": { "id": "9332c282-1fa7-4c42-96ac-58e4e2f88f4c" }
  }'

Returns the same Task structure.

Important: Task records live in the service process's memory, so a restart loses them and tasks/get will no longer find them. Do not treat tasks/get as durable storage — persist anything you need to keep when you first receive it.

Failed response

A failure is not a JSON-RPC level error. You still get result, with status.state set to failed and the reason in status.message:

{
  "jsonrpc": "2.0",
  "id": "9",
  "result": {
    "kind": "task",
    "id": "d091e105-9767-472a-b7e7-5951541cab15",
    "status": {
      "state": "failed",
      "timestamp": "2026-08-12T17:23:56.789Z",
      "message": {
        "kind": "message",
        "role": "agent",
        "parts": [{ "kind": "text", "text": "查询失败:码不存在或无法解析" }]
      }
    }
  }
}

The failure text above reads "query failed: code does not exist or cannot be resolved" — status messages are returned in Chinese.

So check result.status.state to decide success or failure — not the HTTP status code, and not the presence of an error field.

"Code does not exist" and "code exists but is not public" return the same result. This is deliberate: distinguishing them would allow enumeration probing. For a caller, both mean "no readable public entity".

Cancellation

The protocol supports tasks/cancel, but all three Caoliao skills are synchronous queries that have already finished by the time you get a response, so there is no window in which cancelling has any effect.

Known limitations

Limitation	Detail
No streaming	capabilities.streaming is false
No push notifications	capabilities.pushNotifications is false
No state-transition history	capabilities.stateTransitionHistory is false
Tasks are not persisted	tasks/get finds nothing after a restart
Read-only	No writes; actions are completed by a person via humanUrl
Single organization	One call reads one organization's data

Next

• Agent Card and Discovery
• Skills
• Overview