NFT Development Skill

Master NFT development with token standards, metadata design, marketplace integration, and on-chain generative art.

Quick Start

# Invoke this skill for NFT development
Skill("nft-development", topic="standards", standard="ERC721A")

Topics Covered

1. Token Standards

Choose the right standard:

• ERC-721: Standard NFTs, one token per ID
• ERC-721A: Gas-optimized batch minting
• ERC-1155: Multi-token, semi-fungible
• DN404: Divisible NFT hybrid

2. Metadata Design

Structure your NFT data:

• On-chain: Base64 JSON, SVG
• IPFS: Content-addressed storage
• Arweave: Permanent storage
• Dynamic: Evolving traits

3. Marketplace Integration

List and sell NFTs:

• OpenSea: Seaport protocol
• Royalties: EIP-2981
• Operator Filter: Royalty enforcement
• Collection Verification: Metadata standards

4. On-Chain Art

Generate art in Solidity:

• SVG Generation: Dynamic shapes
• Seed-based: Deterministic randomness
• Traits: Rarity distribution
• Base64: Data URI encoding

Code Examples

ERC-721A Mint

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import "erc721a/contracts/ERC721A.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract MyNFT is ERC721A, Ownable {
    uint256 public constant MAX_SUPPLY = 10000;
    uint256 public constant PRICE = 0.08 ether;

    error MaxSupplyReached();
    error InsufficientPayment();

    constructor() ERC721A("MyNFT", "MNFT") Ownable(msg.sender) {}

    function mint(uint256 quantity) external payable {
        if (_totalMinted() + quantity > MAX_SUPPLY) revert MaxSupplyReached();
        if (msg.value < PRICE * quantity) revert InsufficientPayment();

        _mint(msg.sender, quantity);
    }

    function _startTokenId() internal pure override returns (uint256) {
        return 1;
    }
}

On-Chain SVG

function tokenURI(uint256 tokenId) public view returns (string memory) {
    uint256 seed = seeds[tokenId];

    string memory svg = string(abi.encodePacked(
        '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 400 400">',
        '<rect width="400" height="400" fill="#', _getColor(seed), '"/>',
        '<circle cx="200" cy="200" r="80" fill="#', _getColor(seed >> 24), '"/>',
        '</svg>'
    ));

    string memory json = string(abi.encodePacked(
        '{"name":"Art #', tokenId.toString(),
        '","image":"data:image/svg+xml;base64,', Base64.encode(bytes(svg)), '"}'
    ));

    return string(abi.encodePacked(
        "data:application/json;base64,",
        Base64.encode(bytes(json))
    ));
}

EIP-2981 Royalties

import "@openzeppelin/contracts/token/common/ERC2981.sol";

contract NFTWithRoyalty is ERC721A, ERC2981 {
    constructor() {
        _setDefaultRoyalty(msg.sender, 500); // 5%
    }

    function supportsInterface(bytes4 interfaceId)
        public view override(ERC721A, ERC2981)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }
}

Metadata Schema

ERC-721 Standard

{
  "name": "Cool NFT #1",
  "description": "A very cool NFT",
  "image": "ipfs://QmXxx.../1.png",
  "animation_url": "ipfs://QmXxx.../1.mp4",
  "external_url": "https://example.com/1",
  "attributes": [
    { "trait_type": "Background", "value": "Blue" },
    { "trait_type": "Rarity", "value": "Legendary" },
    { "display_type": "number", "trait_type": "Power", "value": 100 }
  ]
}

Standard Comparison

Standard	Best For	Gas (1 mint)	Gas (5 mints)
ERC-721	Simple NFTs	~100k	~500k
ERC-721A	PFP collections	~100k	~120k
ERC-1155	Game items	~50k	~80k

Common Pitfalls

Pitfall	Issue	Solution
Metadata not showing	Bad tokenURI	Validate JSON, check CORS
Gas too high	Standard ERC-721	Use ERC-721A for batches
Royalties not paid	Marketplaces ignore	Use operator filter
Reveal broken	Wrong base URI	Test on testnet first

Troubleshooting

"Metadata not showing on OpenSea"

1. Verify tokenURI returns valid JSON
2. Check IPFS gateway accessibility
3. Refresh metadata via API:

curl "https://api.opensea.io/api/v2/chain/ethereum/contract/{addr}/nfts/{id}/refresh"

"Batch mint out of gas"

• Use ERC-721A instead of ERC-721
• Limit batch size to 10-20 per tx

"Royalties not enforced"

Implement operator filter:

import "operator-filter-registry/src/DefaultOperatorFilterer.sol";

function setApprovalForAll(address op, bool approved)
    public override onlyAllowedOperatorApproval(op)
{
    super.setApprovalForAll(op, approved);
}

Gas Optimization

Technique	Savings
ERC721A batching	~80% for batches
Merkle whitelist	~50% vs mapping
Packed storage	~20k per slot
Custom errors	~200 per error

Cross-References

• Bonded Agent: 07-nft-development
• Related Skills: solidity-development, web3-frontend

Resources

• ERC-721: eips.ethereum.org/EIPS/eip-721
• ERC-721A: erc721a.org
• OpenSea Metadata: docs.opensea.io/docs/metadata-standards

Version History

Version	Date	Changes
2.0.0	2025-01	Production-grade with standards, on-chain
1.0.0	2024-12	Initial release