> ## Documentation Index
> Fetch the complete documentation index at: https://docs.utexo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Mint API Reference

> Network-agnostic REST API for discovering supported networks, estimating fees, initiating transfers, and tracking settlement across EVM, RGB, and RGB Lightning networks.

## Overview

The **Utexo Mint API** is a network-agnostic REST interface for cross-network asset transfers. Clients must discover the networks currently connected to an environment with `GET /networks` instead of hardcoding network availability.

USDT0 settles natively on Arbitrum, which acts as the hub; Ethereum, Tron, and Solana reach that hub through LayerZero. **Arbitrum is currently the only live network in this environment.**

For now, the only tested and available route is Arbitrum (mainnet) to Bitcoin (Utexo signet). Bitcoin mainnet is not available yet.

<Info>
  **Base URL (testnet / dev):** `https://transfer.dev.utexo.com/api/v0`

  All paths in this reference are relative to the base URL. A mainnet base URL will be provided separately. Contact the Utexo team for production endpoint access.
</Info>

The API is stateless and JSON-based. GET requests need no authentication. The `POST /transfers/verify-bridge-in` and `POST /transfers/submit-transaction` endpoints need a signature in the request body (see Authentication).

***

## Transfer Flows

Understanding the transfer direction is essential before making any API calls. The API supports two directions:

<Info>
  **RGB and Lightning destinations:** The RGB-side destination is selected by `networkId`. Use `36` (mainnet) or `91` (testnet) for plain RGB, and `94` (mainnet) or `95` (testnet) for RGB Lightning. The destination accepts an RGB invoice (`rgb:…`) for plain RGB or a Lightning invoice string for RGB Lightning. Network ID `96` identifies Utexo and is not a Lightning network ID.
</Info>

### EVM → RGB or RGB Lightning

Move assets from an EVM network to a plain RGB or RGB Lightning destination.

<Steps>
  <Step title="Discover networks and tokens">
    `GET /networks` — list all connected networks.

    `GET /networks/{network-id}/supported-tokens` — list tokens supported on a given network.
  </Step>

  <Step title="Estimate fees">
    `GET /transfers/estimate/{sender-network}/{recipient-network}/{token-id}/{amount}` — get fee and confirmation time estimate before committing.
  </Step>

  <Step title="Pre-register the transfer">
    `POST /transfers/bridge-in-signature` — pre-register the transfer. Returns a `transferId`, fee estimation, and an empty signature (`0x`).
  </Step>

  <Step title="Call fundsIn() on the EVM contract">
    The user calls `fundsIn()` directly on the EVM bridge contract using the data returned in Step 3. This step happens **client-side** — the API does not broadcast this transaction.
  </Step>

  <Step title="Confirm the transaction">
    `POST /transfers/verify-bridge-in` — notify the mint with the on-chain tx hash to confirm the transfer.
  </Step>

  <Step title="Poll transfer status">
    `GET /transfers/{tx}` — poll using the triggering tx hash until the transfer reaches a terminal status (`FINISHED`, `CANCELLED`, or `FAILED`).
  </Step>

  <Step title="Retrieve destination invoice (optional)">
    `GET /transfers/invoice/{tx-id}/{network-id}` — fetch the RGB or Lightning invoice selected by `network-id`.
  </Step>
</Steps>

### RGB or RGB Lightning → EVM

Move assets from a plain RGB or RGB Lightning wallet to an EVM network.

<Steps>
  <Step title="Discover networks and tokens">
    Same as EVM → RGB Step 1.
  </Step>

  <Step title="Estimate fees">
    Same as EVM → RGB Step 2.
  </Step>

  <Step title="Pre-register the transfer">
    `POST /transfers/bridge-in-signature` — returns the invoice for the selected RGB-side network in the `signature` field: an RGB invoice for plain RGB or a Lightning invoice for RGB Lightning.
  </Step>

  <Step title="Send RGB assets">
    The user pays the invoice string returned in Step 3 with the wallet appropriate for the selected RGB or RGB Lightning network.
  </Step>

  <Step title="Confirm the transfer">
    `POST /transfers/verify-bridge-in` — notify the mint that the RGB or Lightning invoice payment has been completed.
  </Step>

  <Step title="Poll transfer status">
    `GET /transfers/{tx}` — poll for status as in the EVM → RGB flow.
  </Step>
</Steps>

***

## Authentication

Read-only endpoints (all `GET` requests) and `POST /transfers/bridge-in-signature` require no authentication header.

The `POST /transfers/verify-bridge-in` and `POST /transfers/submit-transaction` endpoints validate the caller's identity using a cryptographic signature embedded in the request body:

| Field                     | Description                                                   |
| ------------------------- | ------------------------------------------------------------- |
| `authenticationSignature` | Hex-encoded signature proving ownership of the sender address |
| `publicKey`               | Sender address or public key encoded for `networkId`          |

A `401` response indicates an invalid authentication signature. A `403` response indicates the derived sender address does not match the pre-registered transfer.

<Warning>
  The authentication scheme (signing algorithm, message format) is not formally specified in the current API spec. **Validation required** — contact the Utexo team for the canonical signing procedure before implementing.
</Warning>

***

## Endpoints

### Networks

#### `GET /networks` — List Connected Networks

Returns all connected networks. Optionally filter by token, source network, or name.

**Query Parameters**

| Parameter           | Type      | Required | Description                                                                                         |
| ------------------- | --------- | -------- | --------------------------------------------------------------------------------------------------- |
| `token-id`          | `integer` | No       | Filter results to networks that support this token ID. Cannot be combined with `source-network-id`. |
| `source-network-id` | `integer` | No       | Return networks supported by the specified source network. Cannot be combined with `token-id`.      |
| `search`            | `string`  | No       | Filter results by network name (partial match)                                                      |

**Response `200`** — Array of `Network` objects

```json theme={null}
[
  {
    "id": 84,
    "name": "ARBITRUM-ONE",
    "displayName": "Arbitrum One",
    "type": "NT_EVM",
    "bridgeContract": "0x...",
    "gasLimit": 200000,
    "iconLink": "https://...",
    "active": true,
    "explorerBaseUrl": "https://arbiscan.io"
  }
]
```

***

#### `GET /networks/{network-id}/supported-tokens` — List Supported Tokens

Returns a paginated list of tokens supported on a given network. If `token-id` is provided as a query parameter, returns a single `Token` object instead of a paginated response.

**Path Parameters**

| Parameter    | Type      | Required | Description    |
| ------------ | --------- | -------- | -------------- |
| `network-id` | `integer` | Yes      | The network ID |

**Query Parameters**

| Parameter  | Type      | Required | Description                                                         |
| ---------- | --------- | -------- | ------------------------------------------------------------------- |
| `token-id` | `integer` | No       | If set, returns a single `Token` object instead of a paginated list |
| `search`   | `string`  | No       | Filter tokens by name or symbol                                     |
| `limit`    | `integer` | No       | Number of results per page                                          |
| `page`     | `integer` | No       | Page number (1-indexed)                                             |

**Response `200`** — `SupportedTokensResponse`

<Warning>
  The `SupportedTokensResponse` fields are **PascalCase** in the JSON response (e.g., `Tokens`, `Limit`, `PageCount`). This is a Go struct serialization artifact with no `json` tags. Deserialize accordingly.
</Warning>

```json theme={null}
{
  "Tokens": [...],
  "Limit": 20,
  "Offset": 0,
  "PageCount": 3,
  "CurrentPage": 1,
  "TotalCount": 45
}
```

***

#### `GET /networks/{network-id}/balance/{token-id}/{user-address}` — Get User Token Balance

Returns the token balance for a specific user address on a given network.

**Path Parameters**

| Parameter      | Type      | Required | Description                                                                                  |
| -------------- | --------- | -------- | -------------------------------------------------------------------------------------------- |
| `network-id`   | `integer` | Yes      | The network ID                                                                               |
| `token-id`     | `integer` | Yes      | The token ID                                                                                 |
| `user-address` | `string`  | Yes      | User address. For EVM networks, provide a hex-encoded address (with or without `0x` prefix). |

**Response `200`** — `string`

Balance as a human-readable decimal string in token units (e.g., `"100.50"`).

***

#### `GET /networks/{network-id}/fetch-user-tokens/{user-address}` — Fetch User Multitokens

Requests the gateway to fetch the user's multitoken holdings for the specified network and address.

**Path Parameters**

| Parameter      | Type      | Required | Description                                                  |
| -------------- | --------- | -------- | ------------------------------------------------------------ |
| `network-id`   | `integer` | Yes      | Network ID. The handler validates that the ID is registered. |
| `user-address` | `string`  | Yes      | User address encoded for the selected network.               |

**Response `200`** — Empty body. The current handler writes no JSON response on success.

**Error Responses**

| Status | Meaning                                            |
| ------ | -------------------------------------------------- |
| `400`  | Invalid network ID or user address                 |
| `500`  | The gateway could not fetch the user's multitokens |

***

### Transfers

#### `GET /transfers/estimate/{sender-network}/{recipient-network}/{token-id}/{amount}` — Estimate Transfer Fees

Returns a fee and confirmation time estimate for a proposed transfer. Call this before pre-registering to give users a cost preview.

**Path Parameters**

| Parameter           | Type      | Required | Description                                        |
| ------------------- | --------- | -------- | -------------------------------------------------- |
| `sender-network`    | `string`  | Yes      | Sender network name (e.g., `ARBITRUM-ONE`, `RGB`)  |
| `recipient-network` | `string`  | Yes      | Recipient network name                             |
| `token-id`          | `integer` | Yes      | Token ID — the same token is bridged on both sides |
| `amount`            | `string`  | Yes      | Human-readable amount (e.g., `100.5`)              |

**Query Parameters**

| Parameter           | Type     | Required | Description                                  |
| ------------------- | -------- | -------- | -------------------------------------------- |
| `sender-address`    | `string` | Yes      | Sender's address on the sender network       |
| `recipient-address` | `string` | Yes      | Recipient's address on the recipient network |

**Response `200`** — `Estimation`

```json theme={null}
{
  "fee": "0.50",
  "feePercentage": "0.5",
  "stableFee": "0.10",
  "estimatedConfirmationTime": "5 minutes",
  "resultAmount": "99.40",
  "nativeFee": "0.0002",
  "nativeStableFee": "0.0001",
  "totalNativeCommission": "0.0003",
  "nativeTokenSymbol": "ETH",
  "swapResultAmount": "99400000"
}
```

| Field                   | Description                                                     |
| ----------------------- | --------------------------------------------------------------- |
| `fee`                   | Gas fee denominated in the transfer token                       |
| `stableFee`             | Fixed protocol fee in transfer token units                      |
| `feePercentage`         | Protocol fee as a percentage string                             |
| `resultAmount`          | Amount the recipient will receive after fees                    |
| `nativeFee`             | Gas fee in the sender's native token (multi-token transfers)    |
| `nativeStableFee`       | Stable fee in the sender's native token (multi-token transfers) |
| `totalNativeCommission` | Sum of `nativeFee` + `nativeStableFee`                          |
| `nativeTokenSymbol`     | Symbol of the native token used for commissions                 |
| `swapResultAmount`      | Result amount in the recipient token's smallest units           |

***

#### `POST /transfers/bridge-in-signature` — Pre-Register Transfer

Pre-registers a transfer and returns the data needed for the user to initiate the on-chain action.

* **EVM → RGB or RGB Lightning**: Returns `transferId`, fee `estimation`, and an empty `signature` field (`0x`). The user then calls `fundsIn()` on the EVM bridge contract.
* **RGB or RGB Lightning → EVM**: Returns the invoice string for the selected RGB-side network in the `signature` field. The user pays that RGB or Lightning invoice.

**Request Body** — `BridgeInSignatureRequest`

```json theme={null}
{
  "sender": {
    "networkId": 84,
    "networkName": "ARBITRUM-ONE",
    "address": "0xYourEvmAddress"
  },
  "tokenId": 42,
  "amount": "100.5",
  "destination": {
    "networkId": 36,
    "networkName": "RGB",
    "address": "rgb:..."
  },
  "additionalAddresses": []
}
```

| Field                 | Type       | Required | Description                                                |
| --------------------- | ---------- | -------- | ---------------------------------------------------------- |
| `sender`              | `Address`  | Yes      | Sender network, ID, and address                            |
| `tokenId`             | `integer`  | Yes      | Token ID (same token on both chains)                       |
| `amount`              | `string`   | Yes      | Human-readable amount (e.g., `"100.5"`)                    |
| `destination`         | `Address`  | Yes      | Recipient network, ID, and address                         |
| `additionalAddresses` | `string[]` | No       | Additional addresses (use case: TBD — validation required) |

**Response `200`** — `BridgeInSignatureData`

```json theme={null}
{
  "token": "0xTokenContractAddress",
  "amount": "100500000",
  "gasCommission": "50000",
  "destination": { ... },
  "deadline": "1719999999",
  "nonce": 7,
  "transferId": 1024,
  "signature": "0x",
  "transferType": "LP",
  "estimation": { ... },
  "totalCommission": "600000"
}
```

| Field             | Description                                                                                                                          |
| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
| `token`           | EVM token contract address                                                                                                           |
| `amount`          | Transfer amount in **smallest token units** (not human-readable)                                                                     |
| `deadline`        | EVM: UNIX timestamp expiry. RGB: always `"0"`                                                                                        |
| `nonce`           | Nonce for the EVM bridge contract call                                                                                               |
| `transferId`      | Internal transfer ID — store this for use in `verify-bridge-in`                                                                      |
| `signature`       | EVM → RGB/RGB Lightning: `"0x"` (empty). RGB/RGB Lightning → EVM: RGB or Lightning invoice string selected by destination network ID |
| `transferType`    | Transfer routing type — see [Transfer Types](#transfer-types)                                                                        |
| `totalCommission` | Total commission in smallest token units                                                                                             |

***

#### `GET /transfers/cancel-signature/{transfer-id}/{network-id}/{signature}/{public-key}` — Request Cancellation Signature

The route is registered, but cancellation is currently unavailable. The handler returns `501 Not Implemented` before parsing any path parameters or producing a cancellation signature.

**Path Parameters**

| Parameter     | Type      | Required | Description                                        |
| ------------- | --------- | -------- | -------------------------------------------------- |
| `transfer-id` | `integer` | Yes      | Reserved transfer ID segment; not currently parsed |
| `network-id`  | `integer` | Yes      | Reserved network ID segment; not currently parsed  |
| `signature`   | `string`  | Yes      | Reserved signature segment; not currently parsed   |
| `public-key`  | `string`  | Yes      | Reserved public key segment; not currently parsed  |

**Response `501`** — Standard error envelope with the message `cancelling is unavailable`.

<Warning>
  Do not build a cancellation flow against this endpoint until the handler is enabled.
</Warning>

***

#### `POST /transfers/verify-bridge-in` — Confirm Bridge-In Transaction

Notifies the bridge that the user has completed the on-chain or off-chain send action. Must be called after:

* The EVM `fundsIn()` transaction is broadcast (EVM → RGB/RGB Lightning), or
* The RGB or Lightning invoice payment is complete (RGB/RGB Lightning → EVM)

**Request Body** — `VerifyBridgeInRequest`

```json theme={null}
{
  "transferId": 1024,
  "networkId": 84,
  "txHash": "abcdef1234...",
  "publicKey": "0xYourPublicKeyOrAddress",
  "authenticationSignature": "hex-encoded-signature"
}
```

| Field                     | Type      | Required    | Description                                                                                                      |
| ------------------------- | --------- | ----------- | ---------------------------------------------------------------------------------------------------------------- |
| `transferId`              | `integer` | Yes         | Transfer ID from `bridge-in-signature` response                                                                  |
| `networkId`               | `integer` | Yes         | Sender's network ID                                                                                              |
| `txHash`                  | `string`  | Conditional | Network-encoded transaction hash. May be empty when the RGB-side confirmation has no transaction hash to submit. |
| `publicKey`               | `string`  | Yes         | Sender public key or address                                                                                     |
| `authenticationSignature` | `string`  | Yes         | Hex-encoded signature proving address ownership                                                                  |

**Response `200`** — Empty body (`null`). Accepted.

**Error Responses**

| Status | Meaning                                                                              |
| ------ | ------------------------------------------------------------------------------------ |
| `401`  | Authentication signature is invalid                                                  |
| `403`  | Sender address derived from the signature does not match the pre-registered transfer |
| `500`  | Internal server error                                                                |

***

#### `POST /transfers/submit-transaction` — Submit Signed Transaction

Submits signed transaction data for a pre-registered transfer and returns the resulting transaction hash.

**Request Body**

```json theme={null}
{
  "transferId": 1024,
  "networkId": 26,
  "txData": "base64-encoded-transaction",
  "publicKey": "sender-address-or-public-key",
  "authenticationSignature": "hex-encoded-signature"
}
```

| Field                     | Type      | Required    | Description                                                                                                                 |
| ------------------------- | --------- | ----------- | --------------------------------------------------------------------------------------------------------------------------- |
| `transferId`              | `integer` | Yes         | Transfer ID from `POST /transfers/bridge-in-signature`                                                                      |
| `networkId`               | `integer` | Yes         | Network on which the transaction is submitted                                                                               |
| `txData`                  | `string`  | Conditional | Base64-encoded signed transaction data. Non-empty data is currently accepted only for Bitcoin and Concordium network types. |
| `publicKey`               | `string`  | Yes         | Sender address or public key encoded for `networkId`                                                                        |
| `authenticationSignature` | `string`  | Yes         | Hex-encoded signature proving sender ownership                                                                              |

**Response `200`**

```json theme={null}
{
  "txHash": "network-encoded-transaction-hash"
}
```

**Error Responses**

| Status | Meaning                                                                                                                   |
| ------ | ------------------------------------------------------------------------------------------------------------------------- |
| `400`  | Invalid network, sender address, signature encoding, transaction encoding, or unsupported non-empty `txData` network type |
| `401`  | Authentication signature is invalid                                                                                       |
| `403`  | Sender address does not match the pre-registered transfer                                                                 |
| `500`  | Transaction submission failed                                                                                             |

***

#### `GET /transfers/{tx}` — Get Transfer Status

Returns the current state of a transfer identified by its triggering transaction hash. Poll this endpoint after calling `verify-bridge-in` until the transfer reaches a terminal status.

**Path Parameters**

| Parameter | Type     | Required | Description                                             |
| --------- | -------- | -------- | ------------------------------------------------------- |
| `tx`      | `string` | Yes      | Triggering tx hash, hex-encoded **without** `0x` prefix |

**Response `200`** — Array of `Transfer` objects

```json theme={null}
[
  {
    "id": 1024,
    "senderAmount": "100.5",
    "recipientAmount": "99.9",
    "commission": "0.6",
    "status": "FINISHED",
    "createdAt": "2026-06-18T09:00:00Z",
    "sender": { "networkId": 84, "networkName": "ARBITRUM-ONE", "address": "0x..." },
    "recipient": { "networkId": 36, "networkName": "RGB", "address": "rgb:..." },
    "senderToken": { "id": 42, "shortName": "USDT", "longName": "Tether USD", "iconLink": "..." },
    "recipientToken": { ... },
    "triggeringTx": { "networkName": "ARBITRUM-ONE", "hash": "abc123..." },
    "outboundTx": { "networkName": "RGB", "hash": "def456..." }
  }
]
```

**Transfer Status Values**

| Status       | Description                                                      |
| ------------ | ---------------------------------------------------------------- |
| `WAITING`    | Transfer registered, awaiting on-chain confirmation              |
| `CONFIRMING` | On-chain transaction detected, awaiting sufficient confirmations |
| `ETCHING`    | RGB asset inscription in progress                                |
| `FINISHED`   | Transfer completed successfully                                  |
| `CANCELING`  | Cancellation in progress                                         |
| `CANCELLED`  | Transfer was cancelled                                           |
| `FAILED`     | Transfer failed — check `outboundTx` for details                 |

<Info>
  Poll `GET /transfers/{tx}` at a reasonable interval (e.g., every 5–10 seconds). Avoid aggressive polling — the bridge requires Bitcoin confirmations for RGB-leg completions, which may take several minutes.
</Info>

***

#### `GET /transfers/history/{signature-hex}/{pub-key-hex}` — Get Transfer History

Returns a paginated list of transfers associated with a user's address. Identity is proven by providing a signature.

**Path Parameters**

| Parameter       | Type     | Required | Description                                            |
| --------------- | -------- | -------- | ------------------------------------------------------ |
| `signature-hex` | `string` | Yes      | Hex-encoded signature proving address ownership        |
| `pub-key-hex`   | `string` | Yes      | Public key or address encoded for the selected network |

**Query Parameters**

| Parameter    | Type      | Required | Description                                          |
| ------------ | --------- | -------- | ---------------------------------------------------- |
| `offset`     | `integer` | Yes      | Pagination offset (number of records to skip)        |
| `limit`      | `integer` | Yes      | Number of records to return (must be > 0)            |
| `network-id` | `integer` | Yes      | Network ID to filter history by                      |
| `address`    | `string`  | No       | User address — required for Bitcoin native addresses |

**Response `200`** — `Page`

```json theme={null}
{
  "transfers": [...],
  "offset": 0,
  "limit": 20,
  "totalCount": 142
}
```

***

#### `GET /transfers/invoice/{tx-id}/{network-id}` — Get RGB or Lightning Invoice

Returns the invoice associated with a completed or pending transfer. The `network-id` selects plain RGB (`36` mainnet, `91` testnet) or RGB Lightning (`94` mainnet, `95` testnet).

**Path Parameters**

| Parameter    | Type      | Required | Description                                                |
| ------------ | --------- | -------- | ---------------------------------------------------------- |
| `tx-id`      | `integer` | Yes      | Internal transfer ID (from `bridge-in-signature` response) |
| `network-id` | `integer` | Yes      | RGB or RGB Lightning network ID                            |

**Response `200`** — `InvoiceResponse`

```json theme={null}
{
  "invoice": "rgb:..."
}
```

For an RGB Lightning network ID, `invoice` contains the Lightning invoice string instead.

***

## Transfer Types

The `transferType` field in `BridgeInSignatureData` indicates the internal routing mechanism selected for the transfer. Known values:

| Value  | Description                          |
| ------ | ------------------------------------ |
| `LP`   | Liquidity pool route                 |
| `WU`   | Wire-up route                        |
| `CCTP` | Circle Cross-Chain Transfer Protocol |
| `NTV`  | Native token transfer                |
| `MLT`  | Multi-leg transfer                   |
| `BDXS` | Bridge-DEX swap                      |
| `LPN`  | Lightning-pegged native              |

<Warning>
  The semantic definitions of `transferType` values are not formally documented in the API spec. The descriptions above are inferred from naming conventions. **Validation required** — consult the Utexo engineering team before building routing-dependent logic on this field.
</Warning>

***

## Error Responses

All endpoints return a consistent error envelope on failure.

```json theme={null}
{
  "error": "human-readable error message",
  "code": 1
}
```

**Error Codes**

| Code    | Meaning                                       |
| ------- | --------------------------------------------- |
| `1`     | RGB protocol error                            |
| `2`     | User balance error (insufficient funds)       |
| `3`     | System balance error (bridge liquidity issue) |
| `65535` | Other / unclassified error                    |

***

## Data Models

### `Address`

```json theme={null}
{
  "networkId": 84,
  "networkName": "ARBITRUM-ONE",
  "address": "0x..."
}
```

### `Network`

```json theme={null}
{
  "id": 84,
  "name": "ARBITRUM-ONE",
  "displayName": "Arbitrum One",
  "type": "NT_EVM",
  "bridgeContract": "0x...",
  "gasLimit": 200000,
  "iconLink": "https://...",
  "active": true,
  "explorerBaseUrl": "https://arbiscan.io"
}
```

### `Token`

```json theme={null}
{
  "id": 42,
  "shortName": "USDT",
  "longName": "Tether USD",
  "smartContractAddress": "0x...",
  "decimals": 6,
  "iconLink": "https://...",
  "active": true,
  "native": false
}
```

***

## Open Questions & Unresolved Issues

The following items require validation from the Utexo engineering or product team before this reference is considered complete:

1. **Authentication signing procedure** — The message format and signing algorithm for `authenticationSignature` are not defined in the Swagger spec. Developers cannot implement `verify-bridge-in` or `history` without this information.
2. **`transferType` enum semantics** — The values `LP`, `WU`, `CCTP`, `NTV`, `MLT`, `BDXS`, `LPN` appear in the spec enum but are not described. If transfer type affects the caller's required behavior (e.g., approvals, contract calls), this must be documented.
3. **`additionalAddresses` field** — Present in `BridgeInSignatureRequest` but its purpose and expected values are undocumented. Needs clarification.
4. **Mainnet base URL** — The current spec host is empty; `transfer.dev.utexo.com` is the dev/testnet environment. The production base URL must be published before this reference goes external.
5. **`SupportedTokensResponse` PascalCase fields** — Confirmed from the spec (`NOTE: fields are PascalCase`). This is an unusual JSON convention and should be explicitly called out in SDK wrappers or normalized in a future API version.

***

## Glossary

| Term                | Definition                                                                                                                                                                                               |
| ------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **RGB**             | A client-side validated smart contract protocol built on Bitcoin. Assets are issued and transferred using Bitcoin UTXOs as state anchors.                                                                |
| **RGB Invoice**     | A blinded payment request string used to receive RGB assets. Contains blinded UTXO data to preserve receiver privacy.                                                                                    |
| **EVM**             | Ethereum Virtual Machine — the execution environment used by Arbitrum and other compatible chains.                                                                                                       |
| **Bridge Contract** | The EVM smart contract that locks or releases assets on the EVM side of a cross-chain transfer.                                                                                                          |
| **`fundsIn()`**     | The method on the EVM bridge contract the sender calls to deposit assets for minting.                                                                                                                    |
| **transferId**      | The mint's internal identifier for a pre-registered transfer. Used in `verify-bridge-in` and invoice retrieval.                                                                                          |
| **Triggering Tx**   | The transaction or payment event that initiates the mint: the EVM deposit transaction for EVM → RGB/RGB Lightning, the RGB send for RGB → EVM, or the Lightning invoice payment for RGB Lightning → EVM. |
| **UTXO**            | Unspent Transaction Output — the fundamental unit of Bitcoin accounting. RGB asset state is anchored to UTXOs.                                                                                           |