prepare_attachments MCP tool - Murmur

Remote-only. Prepares private attachment slots for spawn or queue_add. Your client uploads the bytes; the MCP server never reads a local file path.

Request

{
  "attachments": [
    {"filename": "screenshot.png", "content_type": "image/png", "size_bytes": 12345}
  ]
}

The caller supplies a nonempty attachments array. Each item requires a file basename, concrete MIME type, and exact byte count between 1 and 104857600. There are no defaults for these fields.

Upload and attach

The response’s uploads array contains, for each file:

Field	Meaning
`upload_url`	The destination for an HTTP PUT of raw file bytes.
`method`	`PUT`.
`headers`	Required upload headers, including the private `Murmur-Upload-Token` capability.
`staged_attachment`	Metadata to pass unchanged to `spawn` or `queue_add`.

Use your own HTTP tool to PUT the raw bytes to each upload_url, with all returned headers and the exact Content-Length. Do not use JSON or multipart encoding. No Authorization header is needed for the upload.
Wait for every upload to succeed.
Pass the returned staged_attachment objects as the staged_attachments array on spawn or queue_add, using the same authenticated MCP session.

The upload capability expires after 15 minutes. Keep it private: do not log it, share it, or put it in a URL. Each staged file can be claimed once. If preparation expires, prepare and upload again. These are private task attachments. For uploading an artifact from a VM’s local disk, use the local upload tool.