create_attachment_upload

Reserve an image/PDF attachment and obtain a short-lived private PUT URL. Upload file bytes directly to uploadUrl using the returned headers, then call complete_attachment. Treat URLs as temporary credentials; do not log them.

Workflow

Access and behavior

Write or Administrator OAuth consent and a member/administrator team role are required. Tools are listed and callable only when the current grant and role permit them. The signed PUT URL lasts five minutes. Upload directly using the returned headers; never forward a Mill cookie or bearer token to storage. Browsers set Content-Type and derive Content-Length from the file body.

Arguments

Argument	Required	Type or meaning
`taskId`	Yes	Task UUID, not its human identifier such as ENG-1.
`fileName`	Yes	string
`contentType`	Yes	image/png, image/jpeg, image/webp, image/gif, application/pdf
`sizeBytes`	Yes	integer
`sha256`	No	string
`idempotencyKey`	No	One logical mutation key, reused unchanged on retries. MCP forwards it as the REST Idempotency-Key header.

Complete input schema

{
  "type": "object",
  "properties": {
    "taskId": {
      "type": "string",
      "format": "uuid",
      "pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$"
    },
    "fileName": {
      "type": "string",
      "minLength": 1,
      "maxLength": 255
    },
    "contentType": {
      "type": "string",
      "enum": [
        "image/png",
        "image/jpeg",
        "image/webp",
        "image/gif",
        "application/pdf"
      ]
    },
    "sizeBytes": {
      "type": "integer",
      "minimum": 1,
      "maximum": 20971520
    },
    "sha256": {
      "type": "string",
      "pattern": "^[A-Fa-f0-9]{64}$"
    },
    "idempotencyKey": {
      "type": "string",
      "minLength": 8,
      "maxLength": 128
    }
  },
  "required": ["taskId", "fileName", "contentType", "sizeBytes"],
  "additionalProperties": false
}

Example call

The client initializes the MCP connection before sending this JSON-RPC call. Example records are fictional.

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "create_attachment_upload",
    "arguments": {
      "taskId": "22222222-2222-4222-8222-222222222222",
      "fileName": "restore-report.pdf",
      "contentType": "application/pdf",
      "sizeBytes": 2048,
      "idempotencyKey": "restore-report-upload-001"
    }
  }
}

Example result

Mill returns this object in structuredContent and normally a JSON text content block (large responses may shorten the text block). A tool failure sets isError; never treat an error as a completed mutation.

{
  "attachmentId": "44444444-4444-4444-8444-444444444444",
  "uploadUrl": "https://storage.example.test/private-upload?signature=example",
  "headers": {
    "Content-Type": "application/pdf",
    "Content-Length": "2048"
  },
  "expiresAt": "2027-01-18T09:30:00.000Z"
}

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API Reference

create_attachment_upload

Workflow

Access and behavior

Arguments

Example call

Example result

​Workflow

​Access and behavior

​Arguments

​Example call

​Example result

​Related reference

Workflow

Access and behavior

Arguments

Example call

Example result

Related reference