Return a task handle for work that outlives one request

When an operation takes longer than a normal request, accept it at once and return a handle the agent can poll, cancel and collect from later, instead of holding the connection open until it times out.

Why

Exports, builds, batch jobs and anything waiting on a human approval run for minutes or hours. If the only interface is a call that blocks until the work is done, the agent's request times out, it cannot tell whether the work happened, and the obvious recovery (call again) starts a second copy. HTTP has had the answer for decades: RFC 9110's 202 Accepted lets a server take a request for a later process without keeping the connection open, and says the response ought to describe the current status and point to a status monitor. Agent protocols now build on that idea. MCP's Tasks extension lets a server answer a tools/call with a task handle instead of a final result, which the client polls with tasks/get and can stop with tasks/cancel. The handle carries a pollIntervalMs that clients should respect and a ttlMs after which the server may discard the task. The A2A specification describes itself as async-first for long-running and human-in-the-loop work: when a call returns immediately, the caller polls, subscribes or receives push notifications. A handle is a credential to someone's work, so the MCP extension requires an authentication and authorization check on every task request.

Do

Return a handle with a status, a suggested poll interval and a retention time, and check the caller's authorization on every lookup.

Don't

Block a request until a long job finishes, or make the agent resubmit the job to learn whether it ran.

Artifact

{
  "resultType": "task",
  "taskId": "786512e2-9e0d-44bd-8f29-789f320fe840",
  "status": "working",
  "createdAt": "2025-11-25T10:30:00Z",
  "lastUpdatedAt": "2025-11-25T10:40:00Z",
  "ttlMs": 60000,
  "pollIntervalMs": 5000
}

Status values: working, input_required, completed, cancelled, failed. Over plain HTTP, the same contract is a 202 Accepted with Location: /v1/jobs/786512e2 pointing at the status resource.