Read-only JSON. No keys, no state mutation — the same posture as the CypherFaucet / TestnetPool APIs. The wallet uses it to quote; the status page uses it for live data. Base URL: https://testnetswap.com/api.

Amounts appear both in display units (e.g. tBTC) and integer satoshis (*_sats) so clients can avoid floating-point drift.

Supported pairs with the current rate, limits, and free liquidity (total minus what's committed to in-flight swaps).

{
  "ok": true,
  "pairs": [
    { "from": "tLTC", "to": "tBTC", "rate": 0.01,
      "min": 0.001, "max": 0.5,
      "min_sats": 100000, "max_sats": 50000000,
      "liquidity_free": 0.00994694, "liquidity_free_sats": 994694,
      "liquidity_unit": "tBTC" },
    { "from": "tBTC", "to": "tLTC", ... }
  ]
}

Query: ?from=tLTC&to=tBTC&amount=0.5. Quotes against free liquidity, so a pending swap never over-commits the pool.

{
  "ok": true,
  "from": "tLTC", "to": "tBTC",
  "send": 0.5, "receive": 0.005,
  "send_sats": 50000000, "receive_sats": 500000,
  "rate": 0.01, "fee": 0,
  "min": 0.001, "max": 0.5
}

On failure: { "ok": false, "reason": "..." } — e.g. below min, above max, or over free liquidity.

Maker health and live liquidity. Drives uptime monitoring and the "maker online" indicator.

{
  "ok": true,
  "maker_online": true,
  "pairs_up": ["tLTC-tBTC", "tBTC-tLTC"],
  "liquidity": {
    "tBTC": { "total": 1000000, "committed": 0, "free": 994694 },
    "tLTC": { "total": 499714, "committed": 0, "free": 499714 }
  },
  "active_swaps": 0,
  "uptime_secs": 76,
  "version": "0.1.0"
}

All responses are read-only and CORS-enabled. The swap itself runs over a separate WSS relay (the wallet talks to the maker directly); this HTTP API is only for discovery and status. The discovery layer is shaped so additional makers could register later, but on testnet there is one maker — see the source.