const r = await mn.api('/writing/layer-compact', { method: 'POST', body: {} });
if (r.error) mn.log(r.error.code, r.error.message);

{
  "schemaVersion": 1,
  "leasesBefore": 0,
  "eventsRemoved": 0,
  "leasesAfter": 0,
  "maxBytes": 65536,
  "note": "Only fully resolved leases whose session exit is recorded were dropped; ink, cards and blanks are untouched.",
  "revision": 0,
  "topicid": "449C1665-E0DD-4A20-9E67-2B0D451F746D",
  "bridgeApiVersion": "0.91",
  "capacity": {
    "bytes": 179,
    "maxEvents": 256,
    "maxBytes": 65536,
    "events": 0
  },
  "bytesBefore": 179,
  "bytesAfter": 179,
  "ownerID": "mn.practice2"
}