A2A agent

The agent signs in the way MCP clients do: OAuth through the drive, with the same consent page and the same limits. An API token works as a bearer token too, with or without limits. The card at /.well-known/agent-card.json lists both, with the OAuth endpoints.

Every request carries A2A-Version: 1.0. A request without it is treated as 0.3, which this agent doesn't speak.

SendMessage starts a task. By default it answers when the task is done. With returnImmediately it answers at once, while the task carries on.

curl https://mcp.freakingfast.io/a2a \
  -H "Authorization: Bearer $TOKEN" \
  -H "A2A-Version: 1.0" \
  -H "Content-Type: application/json" \
  -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "SendMessage",
  "params": {
    "message": {
      "messageId": "b7f0c2d4-5e61-4a8f-9d3b-1c2e4f6a8b90",
      "role": "ROLE_USER",
      "parts": [
        { "text": "When the client sends the raw footage, make a review link for it" }
      ]
    },
    "configuration": { "returnImmediately": true }
  }
}'

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "task": {
      "id": "8d2f0b6e-41c9-4b1e-a2f3-5c7d9e0f1a2b",
      "contextId": "c51e7a90-2b4d-4f6e-8a1c-3d5e7f9a0b1c",
      "status": {
        "state": "TASK_STATE_WORKING",
        "timestamp": "2026-10-01T09:12:44.000Z"
      }
    }
  }
}

GetTask takes an id and an optional historyLength. ListTasks pages through yours, newest first.

CancelTask stops a task that is still working. A task belongs to the credential that started it: another app or token on the same account can't see it.

Tasks that share a contextId are one conversation, and the agent reads the earlier ones before it starts. Leave it out and you get a new one, returned on the task.

A task can't be picked up again once it has finished. Send the follow-up as a new message with the same contextId and no taskId.

When a task needs something that hasn't happened yet, the agent sets it up and waits. The task stays TASK_STATE_WORKING, and picks up again with what happened. It can wait for files to arrive at a request, notes on a review, someone to open a file, files to land in a folder, or an image to finish.

Everything waiting shows under API tokens in the app. Stopping one there cancels its task.

Give a task a webhook and every change to it is posted there: the whole task, without its history, as { "task": … }. Set one with configuration.taskPushNotificationConfig on SendMessage, or later with CreateTaskPushNotificationConfig.

POST https://your-app.example/hooks/a2a
Content-Type: application/json
X-A2A-Notification-Token: the token you gave
Authorization: Bearer the credentials you gave

{
  "task": {
    "id": "8d2f0b6e-41c9-4b1e-a2f3-5c7d9e0f1a2b",
    "contextId": "c51e7a90-2b4d-4f6e-8a1c-3d5e7f9a0b1c",
    "status": {
      "state": "TASK_STATE_COMPLETED",
      "message": { "role": "ROLE_AGENT", "parts": [{ "text": "The footage is in. Here is the review link." }] },
      "timestamp": "2026-10-02T15:03:10.000Z"
    },
    "artifacts": [{ "artifactId": "…", "name": "Reply", "parts": [{ "text": "…" }] }]
  }
}

• Up to 5 webhooks a task. Tokens and credentials are kept encrypted.
• Redirects aren't followed, and names that point at private addresses are refused as it connects.
• A failed delivery is tried twice more, after 2 and 10 seconds, unless a newer status has gone out since.