CW721 Spec (soulbound): Non Fungible Tokens

CW721 is a specification for non-fungible tokens based on CosmWasm. The name and design is based on Ethereum's ERC721 standard, with some enhancements. The types in here can be imported by contracts that wish to implement this spec, or by contracts that call to any standard cw721 contract.

The specification is split into multiple sections, a contract may only implement some of this functionality, but must implement the base.

Soulbound tokens are implemented by removing transfer and send capabilities.

Base

This handles ownership, and allowances. These must be supported as is by all CW721 contracts. Note that all tokens must have an owner, as well as an ID. The ID is an arbitrary string, unique within the contract.

Messages

Approve{spender, token_id, expires} - Grants permission to spender to operate as spender of the given token. This can only be performed when env.sender is the owner of the given token_id or an operator. There can be multiple spender accounts per token, since the token is soulbound this allows the approved spender to Burn

Revoke{spender, token_id} - This revokes a previously granted permission to Burn the given token_id. This can only be granted when env.sender is the owner of the given token_id or an operator.

ApproveAll{operator, expires} - Grant operator permission to burn all tokens owned by env.sender. This approval is tied to the owner, not the tokens and applies to any future token that the owner receives as well.

RevokeAll{operator} - Revoke a previous ApproveAll permission granted to the given operator.

Queries

OwnerOf{token_id, include_expired} - Returns the owner of the given token, as well as anyone with approval on this particular token. If the token is unknown, returns an error. Return type is OwnerOfResponse. If include_expired is set, show expired owners in the results, otherwise, ignore them.

Approval{token_id, spender, include_expired} - Return an approval of spender about the given token_id. Return type is ApprovalResponse. If include_expired is set, show expired owners in the results, otherwise, ignore them.

Approvals{token_id, include_expired} - Return all approvals that owner given access to. Return type is ApprovalsResponse. If include_expired is set, show expired owners in the results, otherwise, ignore them.

AllOperators{owner, include_expired, start_after, limit} - List all operators that can access all of the owner's tokens. Return type is OperatorsResponse. If include_expired is set, show expired owners in the results, otherwise, ignore them. If start_after is set, then it returns the first limit operators after the given one.

NumTokens{} - Total number of tokens issued

Queries

ContractInfo{} - This returns top-level metadata about the contract. Namely, name and symbol.

NftInfo{token_id} - This returns metadata about one particular token. The return value is based on ERC721 Metadata JSON Schema, but directly from the contract, not as a Uri. Only the image link is a Uri.

AllNftInfo{token_id} - This returns the result of both NftInfo and OwnerOf as one query as an optimization for clients, which may want both info to display one NFT.

Enumerable

Queries

Pagination is achieved via start_after and limit. Limit is a request set by the client, if unset, the contract will automatically set it to DefaultLimit (suggested 10). If set, it will be used up to a MaxLimit value (suggested 30). Contracts can define other DefaultLimit and MaxLimit values without violating the CW721 spec, and clients should not rely on any particular values.

If start_after is unset, the query returns the first results, ordered lexicographically by token_id. If start_after is set, then it returns the first limit tokens after the given one. This allows straightforward pagination by taking the last result returned (a token_id) and using it as the start_after value in a future query.

Tokens{owner, start_after, limit} - List all token_ids that belong to a given owner. Return type is TokensResponse{tokens: Vec<token_id>}.

AllTokens{start_after, limit} - Requires pagination. Lists all token_ids controlled by the contract.