Creating a new buy order

To create a new buy order the user should send a NIP-44 direct message (kind 14) to Mostro with the following decrypted content:

[
  {
    "order": {
      "version": 2,
      "action": "new-order",
      "trade_index": 1,
      "payload": {
        "order": {
          "kind": "buy",
          "status": "pending",
          "amount": 0,
          "fiat_code": "VES",
          "fiat_amount": 100,
          "payment_method": "face to face",
          "premium": 1,
          "created_at": 0
        }
      }
    }
  },
  "<index N signature of the sha256 hash of the serialized first element of content>",
  ["<index 0 pubkey (identity key)>", "<index 0 identity proof signature>"]
]

The nostr event will look like this:

{
  "id": "<Event id>",
  "kind": 14,
  "pubkey": "<Buyer's trade pubkey>",
  "content": "<NIP-44 ciphertext of the content array>",
  "tags": [
    ["p", "<Mostro's pubkey>"],
    ["expiration", "<unix timestamp>"]
  ],
  "created_at": 1234567890,
  "sig": "<Buyer's trade key signature>"
}

Optional: anti-abuse maker bond

When the Mostro node has bonds enabled and apply_to is "make" or "both", the maker must lock a bond before the order is published. Instead of a new-order confirmation, Mostro first responds with a pay-bond-invoice message asking the maker to pay a small hold invoice (typically ~1% of the trade amount). The order is not visible on Nostr until the bond HTLC is accepted.

Only after the maker pays the bond does Mostro:

1. Publish the order to Nostr with status pending.
2. Send the new-order confirmation (shown below).

If the maker never pays the bond invoice it expires and no order is created. See Pay bond invoice — Maker bond for details.

Confirmation message

Mostro will send back a kind 14 event as a confirmation message, the decrypted content looks like the following:

[
  {
    "order": {
      "version": 2,
      "id": "<Order id>",
      "action": "new-order",
      "payload": {
        "order": {
          "id": "<Order id>",
          "kind": "buy",
          "status": "pending",
          "amount": 0,
          "fiat_code": "VES",
          "fiat_amount": 100,
          "payment_method": "face to face",
          "premium": 1,
          "buyer_trade_pubkey": null,
          "seller_trade_pubkey": null,
          "buyer_invoice": null,
          "created_at": 1698870173
        }
      }
    }
  },
  null,
  null
]

Mostro publishes this order as an event kind 38383 with status pending:

[
  "EVENT",
  "RAND",
  {
    "id": "<Event id>",
    "pubkey": "<Mostro's pubkey>",
    "created_at": 1702548701,
    "kind": 38383,
    "tags": [
      ["d", "<Order id>"],
      ["k", "buy"],
      ["f", "VES"],
      ["s", "pending"],
      ["amt", "0"],
      ["fa", "100"],
      ["pm", "face to face"],
      ["premium", "1"],
      ["rating", "[\"rating\",{\"days\":10,\"total_rating\":4.5,\"total_reviews\":7}]"],
      ["network", "mainnet"],
      ["layer", "lightning"],
      ["expiration", "1719391096"],
      ["y", "mostro", "[Mostro instance name]"],
      ["z", "order"]
    ],
    "content": "",
    "sig": "<Mostro's signature>"
  }
]

After a seller takes this order Mostro will request an invoice from the buyer, Mostro will pay the buyer's invoice when the seller releases the funds.

Creating the order with a lightning invoice

There are two ways where the buyer can create the order adding the invoice:

1. If the buyer already knows the amount, e.g. buyer wants to buy 15000 sats with 10 euros, in this case the buyer knows from the beginning that the invoice should have amount 15000 - Mostro's fee, instead of the user doing the calculation, the client must do it and in some cases create the invoice with the right amount.

2. If the buyer don't know the amount, e.g. buyer wants to buy sats with 10 euros, in this case the buyer can add an amountless invoice and Mostro will pay it with the market price amount - Mostro's fee automatically.