Stablecoins

Mostro can trade bitcoin for stablecoins. The coin is the order's currency, in the f tag where a fiat order has its ISO 4217 code, and each coin is pegged 1:1 to a fiat:

Codes are upper-case. The list grows one row per coin; a node prices only the coins it knows.

Price

A node prices a market order in a stablecoin at exactly the price of the fiat it is pegged to. One USDT is one USD, so the BTC price in USDT is the node's BTC price in USD, and the premium applies as usual.

Pricing a stablecoin is the operator's choice:

• A node that quotes a coin publishes it in its exchange rates event, next to the fiat currencies.
• A node that does not quote it refuses market-priced orders in it (amt = 0). It may still accept fixed-price ones, if fiat_currencies_accepted allows the code.

Clients SHOULD offer market price for a stablecoin only when the node's exchange rates event carries its code.

Amounts are whole units, as for fiat: fa is 100, not 100.50.

Network

The same coin exists on several networks, and a transfer sent on the wrong one can be lost. The order names the network in its payment method:

["f", "USDT"],
["fa", "100"],
["pm", "USDT (Tron)", "USDT (Liquid)"]

Clients SHOULD write each method as <CODE> (<Network>), with the network names below, so that the same network is spelled the same way in every order and the order book can be filtered by it. An order may list several networks; the buyer says in the chat which one they will use.

A network not listed here is written with its common name. The daemon does not check pm; it publishes the methods as written.

Settlement and disputes

The trade runs as with fiat: the buyer sends the coin, then sends fiat-sent, and the seller releases once it has arrived.

• The sender pays the network fee. The seller must receive the full fa amount.
• The buyer SHOULD paste the transaction id in the peer chat. On a public chain it is what a solver checks in a dispute: the network, the recipient, the amount and the confirmations.

Compatibility

f is NIP-69's tag, defined there as an ISO 4217 code. A NIP-69 client that checks for one will likely skip orders in a stablecoin.