const r = await mn.api('/writing/content', {
  method: 'POST',
  body: {
    carrier: 'blank',
    storageTopicId: topicid,
    physicalBlankId: blankId
  }
});
mn.log(r.ready, r.hasVisibleContent);

{
  "schemaVersion": 1,
  "hasVisibleContent": null,
  "layerSettings": {
    "liveWindowVerified": false,
    "registeredLayerIds": [],
    "savedOverlayLayerId": "",
    "savedActiveLayerId": "",
    "bindTextImageToSketchLayer": false
  },
  "layerIds": null,
  "inventoryState": "no-stored-records",
  "bridgeApiVersion": "0.91",
  "recordCounts": {},
  "scope": {
    "carrier": "focus",
    "focusNoteId": "D3085422-2CB9-4B68-A78D-DEE351CF9C38",
    "storageTopicId": "449C1665-E0DD-4A20-9E67-2B0D451F746D"
  },
  "projectionFingerprint": "19a2274c021d9eb50eb0af8d7b0ad7c86a71065b9c8262a786778f3e19b7cb6c",
  "hostRowCount": 0,
  "readOnly": true,
  "parts": [],
  "warnings": [
    "Inventory counts records, not strokes, visible ink, saved attempts or completed answers.",
    "Layer IDs are stored associations, not current visibility; unbound text/images and legacy strokes may remain visible.",
    "The projection fingerprint is diagnostic, not a content revision or compare-and-swap token.",
    "Direct blank/card body is outside the layer inventory. Media is neither loaded nor downloaded."
  ],
  "hostNoteIds": [],
  "includesUnsavedCanvas": false,
  "consistency": "persisted-snapshot",
  "repairsPerformed": false
}