NEP-24: Royalty Standard

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NEP-24 specifies a royaltyInfo method for NEP-11 NFTs so marketplaces can fetch royalty recipients and amounts for secondary sales. Unlike ERC-2981 which returns a single recipient, NEP-24 supports multiple royalty recipients in a single response.

Spec: NEP-24 Proposal

Interface

Method	Parameters	Return	Description
royaltyInfo	ByteArray tokenId, Hash160 royaltyToken, Integer salePrice	Array<[Hash160, Integer]>	Royalty recipients and amounts

interface INEP24Royalty {
    struct RoyaltyInfo {
        address royaltyRecipient;
        uint256 royaltyAmount;
    }

    function royaltyInfo(bytes32 tokenId, address royaltyToken, uint256 salePrice)
        external view returns (RoyaltyInfo[] memory);
}

Key Differences from ERC-2981

	ERC-2981 (Ethereum)	NEP-24 (Neo)
Return type	Single (address, uint256)	Array of [recipient, amount] pairs
Multiple recipients	No — single recipient only	Yes — split royalties natively
Royalty token	Implied (same as sale token)	Explicit royaltyToken parameter
Basis points	10000 = 100%	10000 = 100%
Interface detection	supportsInterface(0x2a55205a)	Manifest supportedstandards: ["NEP-24"]

Royalty Token Parameter

The royaltyToken parameter specifies which token royalties should be paid in (e.g., GAS, a specific NEP-17 token). This is reserved for future use in the devpack's minimal implementation but enables token-specific royalty rules.

Implementation Example

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

import "standards/NEP11.sol";
import "standards/NEP24.sol";
import "libraries/Runtime.sol";

/// @title RoyaltyNFT — NEP-11 NFT with NEP-24 royalties
contract RoyaltyNFT is NEP11, NEP24Royalty {

    constructor()
        NEP11("Royalty NFT", "RNFT", 0, "", 10000, false)
    {
        // Set default royalty: 5% (500 basis points) to deployer
        _setDefaultRoyalty(msg.sender, 500);
    }

    /// @dev Mint with per-token royalty override
    function mintWithRoyalty(
        address to,
        bytes32 tokenId,
        bytes memory props,
        address royaltyRecipient,
        uint96 royaltyBps
    ) external onlyMinter {
        require(Runtime.checkWitness(msg.sender), "unauthorized");
        mint(to, tokenId, props);

        // Override default royalty for this specific token
        if (royaltyRecipient != address(0) && royaltyBps > 0) {
            _setTokenRoyalty(tokenId, royaltyRecipient, royaltyBps);
        }
    }

    /// @dev Query royalty info — returns array of [recipient, amount] pairs
    /// For a sale of 100 GAS with 5% royalty: returns [(creator, 5 GAS)]
    function royaltyInfo(bytes32 tokenId, address royaltyToken, uint256 salePrice)
        public view override returns (RoyaltyInfo[] memory)
    {
        return super.royaltyInfo(tokenId, royaltyToken, salePrice);
    }
}

The NEP24Royalty abstract contract provides:

Internal Method	Description
_setDefaultRoyalty(recipient, bps)	Set fallback royalty for all tokens
_setTokenRoyalty(tokenId, recipient, bps)	Override royalty for a specific token
_clearTokenRoyalty(tokenId)	Remove per-token override, fall back to default
_getRoyaltyRule(tokenId)	Get effective royalty rule (per-token or default)

Basis Points Validation

The devpack enforces bps <= 10000 and recipient != address(0). Setting invalid values reverts with NEP24InvalidRoyaltyBps or NEP24InvalidRoyaltyRecipient.