Token Metadata Schema

A schema enforces a consistent structure for essential token properties, ensuring universal readability. Key fields include:

• Name: The human-readable identifier (e.g., "Chainscore Governance Token").
• Symbol: The ticker symbol (e.g., "CSCORE").
• Decimals: The divisibility of the token, defining its smallest unit.
• Total Supply: The fixed or dynamic total number of tokens in existence. This standardization is foundational for wallets to display balances and for exchanges to list assets.

Beyond core data, schemas support rich, descriptive metadata crucial for NFTs and branded tokens. This includes:

• Description: A detailed explanation of the token's purpose or the NFT's artwork.
• Image/Animation URI: A pointer to the visual or media asset representing the token.
• External URL: A link to a project's website or the NFT's dedicated page.
• Attributes/Properties: Key-value pairs for traits (e.g., {"rarity": "Legendary", "background": "Space"}).

Metadata is typically stored off-chain for efficiency, with the on-chain token contract holding a Uniform Resource Identifier (URI) pointer. Common storage solutions include:

• IPFS (InterPlanetary File System): A decentralized protocol using Content Identifiers (CIDs) for immutable, permanent storage.
• Arweave: A blockchain-like protocol designed for permanent, low-cost data storage.
• Centralized HTTPS: A traditional web server, which introduces a single point of failure and mutability risk.

Widely adopted schemas are defined by Ethereum Request for Comments (ERC) standards, creating a common language across the ecosystem.

• ERC-20: The foundational standard for fungible tokens, defining a basic metadata interface.
• ERC-721: The standard for non-fungible tokens (NFTs), adding unique token IDs and richer metadata extensions.
• ERC-1155: A multi-token standard that can represent both fungible and non-fungible assets within a single contract, with efficient batch operations.

Schemas define where and how data is stored, a critical design choice.

• On-Chain Metadata: All data is stored directly in the smart contract's storage. This guarantees permanence and availability but is extremely gas-intensive and immutable.
• Off-Chain Metadata: Only a URI hash is stored on-chain, pointing to a JSON file hosted elsewhere. This is cost-effective and flexible but relies on the persistence of the external data source (e.g., IPFS, Arweave).

A robust schema enables the verification of a token's authenticity and history. This is achieved through:

• Immutable Links: Using decentralized storage (IPFS CIDs) creates a tamper-proof connection between the token ID and its metadata.
• Signature Verification: Metadata can include cryptographic signatures from the creator to prove authorship.
• Chain of Custody: For NFTs, the transaction history on the blockchain provides a public, verifiable record of ownership transfers from the original mint.

These fields uniquely identify the token and its basic attributes.

• name: The human-readable title of the token (e.g., "Chainscore Governance Token").
• symbol: The abbreviated ticker symbol (e.g., "CSCORE").
• description: A detailed explanation of the token's purpose, utility, or the asset it represents.
• image: The URI pointing to the token's visual representation, such as a logo or artwork. This is the primary field rendered by wallets and explorers.

Fields that provide additional descriptive context and categorization.

• attributes: An array of objects defining traits or properties (common for NFTs). Each attribute includes trait_type (e.g., "Rarity", "Background") and value (e.g., "Legendary", "Blue").
• properties: A more flexible key-value store for arbitrary data, often used for technical details or links to external files.
• external_url: A link to a website or external page with more information about the token or its project.

Fields that declare adherence to specific metadata standards, ensuring compatibility.

• Standard Identifiers: Fields like erc721 or erc1155 metadata may be included to signal the token type.
• schema or standard: May specify the exact metadata schema version used (e.g., referencing a specific IPFS hash of the schema definition).
• Compliance with these fields allows marketplaces like OpenSea (using OpenSea Metadata Standards) or wallets to correctly parse and display the token.

Fields that define economic rights and attribution, crucial for creator economies.

• seller_fee_basis_points: The royalty percentage (e.g., 500 for 5%) owed to the creator on secondary sales.
• fee_recipient: The wallet address that receives royalty payments.
• creators: An array listing the artists or developers involved, often including their addresses and contribution shares. These fields are foundational for platforms like Manifold or Foundation.

Fields for tokens that are dynamic or have multiple media components.

• animation_url: A URI to a multi-media asset (e.g., HTML page, MP4 video, 3D model) that represents the token. Takes precedence over the image field in supporting viewers.
• youtube_url: A link to a related YouTube video.
• background_color: A hex color code (e.g., "#FFFFFF") for the background of the token's display card in some marketplaces.

A concrete example showing how these fields come together in a standard like ERC-721.

jsonCopy
{
  "name": "Galactic Ape #123",
  "description": "A unique ape explorer from the Galactic Ape Collection.",
  "image": "ipfs://QmXx.../ape123.png",
  "external_url": "https://galacticapes.io/ape/123",
  "attributes": [
    { "trait_type": "Background", "value": "Nebula" },
    { "trait_type": "Fur", "value": "Gold" }
  ]
}

The on-chain token's tokenURI() method returns a link (URI) to this JSON document.

A standard schema defines essential fields for token identification and presentation. Key fields include:

• name: The human-readable name of the token (e.g., "Wrapped Ether").
• symbol: The ticker symbol (e.g., "WETH").
• decimals: The number of decimal places used to represent token amounts.
• description: A textual description of the token's purpose.
• image: A URI pointing to a logo or artwork representing the token.

For NFTs, metadata schemas are more complex, defining unique attributes. The ERC-721 Metadata JSON Schema and ERC-1155 Metadata URI standards specify fields like:

• tokenId: The unique identifier of the NFT.
• attributes: An array of trait objects (e.g., {"trait_type": "Background", "value": "Blue"}) used for rarity and display.
• animation_url: A URI to multimedia content (e.g., HTML, video). These are typically stored off-chain (e.g., on IPFS) and referenced by a URI in the smart contract.

Due to cost and size limitations, detailed metadata is rarely stored directly on-chain. Instead, a JSON file following the schema is stored off-chain on decentralized storage like IPFS or Arweave. The smart contract stores only a base URI or a token-specific URI (like ipfs://QmX.../1.json) that points to this file. This ensures data permanence and decentralization, critical for the longevity of NFTs.

The primary on-chain interface for retrieving metadata. In ERC-721 and ERC-1155 contracts, the tokenURI(uint256 tokenId) function returns a URI (Uniform Resource Identifier) pointing to the token's JSON metadata file. Wallets and marketplaces call this function to fetch and render the token's name, image, and attributes. A broken or incorrect tokenURI will cause the token to appear as "broken" in user interfaces.

For fungible tokens (ERC-20), decentralized schemas like the Token Lists standard aggregate metadata for easier discovery. A Token List is a JSON file containing an array of token definitions, each with the standard schema fields (name, symbol, decimals, logoURI). Projects like Uniswap and CoinGecko maintain lists, allowing DApps to pull verified token logos and info without relying on centralized APIs.

A standardized schema is crucial for ecosystem interoperability. It allows:

• Wallets (MetaMask, Rainbow) to display consistent token information.
• Marketplaces (OpenSea, Blur) to list and filter NFTs by attributes.
• Analytics Tools to index and categorize token data correctly.
• Bridges & Wrappers to preserve metadata when moving assets across chains. Without it, each application would need custom parsers, fragmenting the user experience.

A primary vulnerability is a centralized metadata URI (e.g., https://example.com/token/1.json). If the host server is compromised, goes offline, or changes the data, the token's properties can be altered or lost. This breaks the immutability guarantee of the underlying blockchain. Mitigations include using IPFS or Arweave for decentralized storage, or implementing on-chain metadata for critical attributes.

Applications must validate the structure and content of fetched metadata to prevent injection attacks or malformed data from crashing systems. Key practices include:

• JSON Schema Validation: Enforcing a strict schema (like ERC-721's optional metadata extension) to ensure required fields (name, image) are present and correctly typed.
• Content Hash Verification: Using a hash field within the metadata to verify the integrity of linked image or animation files, ensuring they haven't been tampered with after publication.

Malicious metadata can be used in social engineering attacks. A common vector is a malicious external_url or image field that points to a phishing site or loads harmful content into a wallet's or marketplace's UI. Wallets and explorers must sanitize and carefully render all metadata fields, treating them as untrusted user input. The ERC-721 Metadata Standard recommends that clients protect users from potentially harmful media.

Some token standards (e.g., ERC-721 with a baseURI) allow for metadata updates, creating a trust assumption about the contract owner. A malicious or compromised owner can change the metadata for all tokens. Freezable metadata is a feature where a permanent, immutable hash is stored on-chain after finalization. Projects should clearly communicate their metadata mutability policy (immutable, owner-updatable, decentralized).

Reliability depends on the availability of metadata servers. Slow or rate-limited centralized APIs can degrade application performance. Decentralized storage like IPFS relies on a robust pinning service and gateway infrastructure to ensure high availability. Best practices include:

• Using redundant gateways (e.g., Cloudflare's IPFS gateway, public.ipfs.io).
• Implementing client-side caching with appropriate TTLs to reduce fetch latency and load.

A lack of schema standardization forces each application (wallets, marketplaces, explorers) to implement custom parsing logic, increasing the attack surface and potential for errors. Widely adopted standards like ERC-721 Metadata JSON Schema and ERC-1155 Metadata URI provide a reliable baseline. Extensions for traits (ERC-721A), royalties (ERC-2981), and other properties should be integrated following established patterns to ensure cross-platform compatibility and security.