“Treasure Chest” by FateDenied is licensed under CC BY-NC 2.0.

tzNFT: Non-fungible Tokens on Tezos

Recently, we released a new version of the tzNFT command line tool and a corresponding tutorial describing how to use it. The NFT tutorial gives detailed step-by-step instructions on how to prepare your data, originate an NFT collection smart contract, and mint tokens. It also provides documentation on all tzNFT commands. In this post we will just give an overview of the minting process and discuss some tool options.

The new tzNFT CLI now fully supports the most recent Tezos metadata standards (TZIP-016 and TZIP-021).

There are plenty of resources that explain what non-fungible tokens are (like here and here). If you want a deep dive into what NFTs are and even how to build your own NFT platform on Tezos, we encourage you to read this post. tzNFT provides a high-level CLI API, which you could use right from the command line or from other scripts. Besides the tzNFT tool, we also provide a reusable high-level programmatic API to interact with FA2 contracts (fa2-interfaces). Use it to create your own applications that interact with FA2 smart contracts.

Things You Should Probably Know Before Creating Your Own NFTs

Before diving into technical details, let’s take a 10,000 foot view at all the moving parts and terminology.

Token Smart Contract

A token on the blockchain is just a record of ownership telling which Tezos address owns a token with a particular ID. Each token collection is represented by a smart contract that keeps a ledger of such records for all of its tokens and their current ownership. A collection smart contract also has some standard entry points (API) which allow one to transfer token ownership and inspect the collection. There is a Tezos standard TZIP-012 (also known as FA2) specifying a unified token contract interface and metadata. tzNFT provides the implementation of the collection smart contract that conforms to the TZIP-012.

Smart Contract Metadata

When a token contract is originated on blockchain, we also want to provide a description of that contract and token collection. We can do that by providing contract metadata at the time of the contract origination. TZIP-016 Tezos standard describes the format of the contract metadata. Here is a list of the most important attributes:

• name — name of the NFT collection
• description— optional description of the NFT collection
• homepage — link to the NFT project homepage
• authors — list of the NFT collection authors
• version — version of the smart contract
• license — smart contract license
• interfaces — list of Tezos standards (interfaces) implemented by the smart contract. For our NFT collection implementation we support TZIP-016, TZIP-012, TZIP-021

tzNFT can generate a template metadata file and validate if the file format conforms to the TZIP-016 standard.

Rich Token Metadata

Besides a token ID, each NFT has associated metadata which describes what a token is. The FA2 standard requires a token to have at least the name attribute. TZIP-021 Tezos standard describes rich token metadata format. You can specify some of the standard metadata attributes and even add custom ones. Here is a list of the most important attributes:

• name — the name of the NFT
• description — optional description of this NFT
• decimals — always set to 0for NFTs
• isBooleanAmount — always set to true for NFTs
• artifactUri — the link to a digital asset representing the NFT. If the asset is hosted on IPFS, the link should have the following format ipfs://<ipfs_hash?/<optional_path>. Often a digital asset is an image, but it can be any media type.
• displayUri — the link to the image representing this NFT
• thumbnailUri — the link to the thumbnail version of the image representing this NFT

When minting (creating) a new token, we need to provide a JSON file with the token metadata. tzNFT can generate a template metadata file and validate if the file format conforms to the TZIP-021 standard.

Why TZIP?

Using NFT smart contracts that conform to the TZIP-012, TZIP-016 and TZIP-021 standards makes your tokens discoverable by various other applications and tools such as wallets and NFT marketplaces.

From Images to an NFT Collection on Tezos

There are several ways to associate media with NFTs. The approach that tzNFT takes is to store both your digital assets (images) and token metadata on IPFS using Pinata (You may use other IPFS services or even not use IPFS at all).

The general steps are:

1. Install tzNFT tool by running npm install -g @oxheadalpha/tznft.
2. Create a new NFT project directory and run tznft init. This will create a tznf.json config file with all the settings for your project. Beware if you are using Tezos mainnet, this file will also hold your Tezos private keys.
3. Prepare your NFT collection metadata.
   – Run tznft create-collection-meta to generate the metadata template JSON file.
   – Edit collection metadata and validate it with tznft validate-collection-meta.
4. Originate a new collection smart contract using the collection metadata created in the previous step by running tznft create-collection.
5. Prepare your digital assets (images).
6. Pin (upload) your digital assets on IPFS. You can either pin every file individually or pin the whole directory that contains your assets (there are tznft pin-file and tznft pin-dir commands).
7. Use your asset’s IPFS URLs to prepare your token metadata. If you pinned your files individually your IPFS URLs should have the form ipfs://<ipfs_hash_for_asset_file>. If you pinned the whole directory your IPFS URL will be in the form of ipfs://<ipfs_hash_for_dir>/<path_to_file_in_dir>.
   – Generate token metadata template JSON file by running tznft create-nft-meta.
   – Edit token metadata attributes (artifactUri attribute should link to the NFT image on IPFS) and create a separate metadata JSON file for each token you intend to mint.
8. Pin (upload) your token metadata files to IPFS. You can pin metadata files individually or pin the whole directory.
9. Mint tokens. Run tznft mint or tznft mint-from-file. Provide a new ID and IPFS metadata URL for each token. You can mint multiple token batches into the same NFT collection contract.
10. Freeze your token collection by running tznft mint-freeze. After freezing the collection, no more new tokens can be minted. This optional step may guarantee the NFT’s scarcity and signal to other users that the collection has a limited token supply.

You can do a “dry run” first using either Tezos sandbox (default tzNFT option) or a testnet. Once you are ready, you can switch to Tezos mainnet, configure a funded Tezos address and mint your NFTs on the mainnet.

What is Next?

Now you have created your own NFT collection smart contract on Tezos. You can inspect and transfer your tokens either by using tznft show-meta and tznft show-balance commands; TZComet or other Tezos indexer and wallet applications.

In the tutorial we created non-fungible tokens that represent images hosted on IPFS. It is also possible to link to other media types such as documents, video, or audio by modifying the token metadata (check media formats definition in the TZIP-021 standard).

Since we followed the Tezos FA2 token standard, your contract can be used by any other contract or application which interacts with FA2 tokens.
For instance, you may onboard your contract at Objkt.com or Rarible marketplaces and list them for sale.

You can create your own scripts that automate NFT generation and use tzNFT CLI tool there. You can even create your own NFT platform from scratch with the reusable FA2 API package