NFT Development Marketplace Royalty Standards (EIP-2981) Questions and Answers 1 — Questions and Answers
Question 1: An NFT marketplace is processing a sale and needs to determine if it should pay royalties for a given token. According to the EIP-2981 standard, what is the first step the marketplace's smart contract should take to check for royalty information?
- Call the `getRoyaltyInfo` function with the `tokenId` and `salePrice`.
- Attempt to transfer 1 wei to a standardized royalty treasury address.
- Check if the token contract supports the EIP-2981 interface ID (0x2a55205a) via an ERC-165 check. (Correct answer)
- Query a centralized, off-chain registry managed by a consortium of marketplaces.
Correct answer: Check if the token contract supports the EIP-2981 interface ID (0x2a55205a) via an ERC-165 check.
EIP-2981 is designed to be discoverable through the ERC-165 standard. Before calling `royaltyInfo`, a compliant marketplace should first call `supportsInterface(0x2a55205a)` on the NFT contract to confirm it implements the royalty standard, ensuring predictable behavior and preventing failed calls.
Question 2: A developer implements the EIP-2981 `royaltyInfo` function for an NFT collection. For a token with ID `123`, a 5% royalty is due. If this token sells for 10 ETH, what should the `royaltyInfo(123, 10 ether)` function return?
- A single address and a `royaltyAmount` of `500`.
- An array of recipient addresses and an array of corresponding amounts.
- The royalty percentage (`5`) and the recipient address.
- A `receiver` address and a `royaltyAmount` of `0.5 ether`. (Correct answer)
Correct answer: A `receiver` address and a `royaltyAmount` of `0.5 ether`.
The `royaltyInfo` function takes the `_tokenId` and the `_salePrice` as arguments and must return two values: the `receiver` address and the calculated `royaltyAmount`. The `royaltyAmount` should be in the same denomination as the `_salePrice`, so for a 10 ETH sale with a 5% royalty, the amount is 0.5 ETH.
Question 3: What is the core purpose of the EIP-2981 standard in the NFT ecosystem?
- To enforce royalty payments on every `transferFrom` call, preventing unpaid transfers.
- To provide a universal, on-chain method for signaling royalty information to any marketplace or participant. (Correct answer)
- To create a decentralized governance system for setting and updating royalty percentages.
- To automatically split royalty payments among multiple collaborators directly within the token contract.
Correct answer: To provide a universal, on-chain method for signaling royalty information to any marketplace or participant.
EIP-2981's primary goal is to standardize how royalty information is communicated. It doesn't enforce payments but provides a single, queryable function (`royaltyInfo`) on the NFT contract itself, allowing any third party (like a marketplace) to retrieve the intended royalty recipient and amount for a given sale.
Question 4: A digital art collective wants to release an NFT where the 10% royalty fee is split equally between the lead artist and a charity. How can this be achieved while remaining compliant with the EIP-2981 standard?
- The `royaltyInfo` function must be modified to return an array of two addresses and the corresponding amounts.
- This is not possible, as EIP-2981 only supports a single royalty recipient.
- The `royaltyInfo` function should return the address of a separate payment splitter smart contract as the `receiver`. (Correct answer)
- The NFT must be listed exclusively on marketplaces that have proprietary, multi-recipient royalty features.
Correct answer: The `royaltyInfo` function should return the address of a separate payment splitter smart contract as the `receiver`.
EIP-2981 specifies that `royaltyInfo` must return a single `receiver` address. To handle splits, the standard practice is to deploy a separate payment splitter contract. The NFT's `royaltyInfo` function then returns the address of this splitter contract. The marketplace sends the full royalty amount to the splitter, which then handles the logic of distributing the funds to the multiple beneficiaries.
Question 5: Which of the following statements accurately describes the role of marketplaces regarding EIP-2981?
- Marketplaces are required by the standard to block the sale of any NFT that does not implement EIP-2981.
- The standard forces marketplace contracts to automatically execute the royalty payment in the same transaction as the sale.
- EIP-2981 is a voluntary standard, and enforcement of the signaled royalties is a policy decision made by each individual marketplace. (Correct answer)
- Once a marketplace supports EIP-2981, they must honor the royalty percentage, even if it exceeds their platform's maximum fee limit.
Correct answer: EIP-2981 is a voluntary standard, and enforcement of the signaled royalties is a policy decision made by each individual marketplace.
EIP-2981 is a signaling mechanism, not an enforcement mechanism. The standard itself cannot force a marketplace to pay royalties. It simply provides the data. Whether a marketplace honors these on-chain royalties is a business and policy decision, leading to the current landscape where royalty enforcement varies across different platforms.
Question 6: A developer is implementing EIP-2981 and sets a royalty of 2.5%. The `royaltyInfo` function is called with a `_salePrice` of 1,500 wei. Given that Solidity does not handle floating-point numbers, how should the `royaltyAmount` be calculated to avoid precision loss?
- By calculating `(1500 * 2.5) / 100` directly in the function.
- By calculating `(1500 * 25) / 1000` to represent 2.5%.
- By calculating `(1500 * 250) / 10000` using basis points. (Correct answer)
- By requiring the `_salePrice` to be a multiple of 100.
Correct answer: By calculating `(1500 * 250) / 10000` using basis points.
The common and recommended practice for handling percentage calculations in Solidity is to use basis points, where 1 basis point = 0.01%. Therefore, a 2.5% royalty is represented as 250 basis points. The calculation `(salePrice * 250) / 10000` correctly computes the royalty amount using integer arithmetic, minimizing precision loss.
NFT Development Marketplace Royalty Standards (EIP-2981) Questions and Answers 1
An NFT marketplace is processing a sale and needs to determine if it should pay royalties for a given token.
According to the EIP-2981 standard, what is the first step the marketplace's smart contract should take to check for royalty information?