​
Summary

  • The metadata pointer extension associates a token mint directly to a metadata account. This happens by storing the metadata account’s address in the mint. This metadata account address can be an external metadata account, like Metaplex, or can be the mint itself if using the metadata extension.
  • The metadata mint extension allows embedding of metadata directly into mint accounts through the Token Extensions Program. This is always accompanied with a self-referencing metadata pointer. This facilitates embedding comprehensive token information at the minting stage.
  • These extensions enhance the interoperability of tokens across different applications and platforms by standardizing how metadata is associated and accessed.
  • Directly embedding or pointing to metadata can streamline transactions and interactions by reducing the need for additional lookups or external calls.

​
Overview

The Token Extensions Program streamlines metadata on Nexis Native Chain. Without the Token Extensions Program, developers store metadata in metadata accounts using a metadata onchain program; mainly Metaplex. However, this has some drawbacks. For example the mint account to which the metadata is “attached” has no awareness of the metadata account. To determine if an account has metadata, we have to PDA the mint and the Metaplex program together and query the network to see if a Metadata account exists. Additionally, to create and update this metadata you have to use a secondary program (i.e. Metaplex). These processes introduces vender lock in and increased complexity. Token Extension Programs’s Metadata extensions fix this by introducing two extensions:
  • metadata-pointer extension: Adds two simple fields in the mint account itself: a publicKey pointer to the account that holds the metadata for the token following the Token-Metadata Interface, and the authority to update this pointer.
  • metadata extension: Adds the fields described in the Token-Metadata Interface which allows us to store the metadata in the mint itself.

​
Metadata-Pointer extension:

Since multiple metadata programs exist, a mint can have numerous accounts claiming to describe the mint, making it complicated to know which one is the mint’s “official” metadata. To resolve this, the metadata-pointer extension adds a publicKey field to the mint account called metadataAddress, which points to the account that holds the metadata for this token. To avoid imitation mints claiming to be a stablecoin, a client can now check whether the mint and the metadata point to each other. The extension adds two new fields to the mint account to accomplish this:
  • metadataAddress: Holds the metadata account address for this token; it can point to itself if you use the metadata extension.
  • authority: The authority that can set the metadata address.
The extension also introduces three new helper functions:
  • createInitializeMetadataPointerInstruction
  • createUpdateMetadataPointerInstruction
  • getMetadataPointerState
The function createInitializeMetadataPointerInstruction will return the instruction that will set the metadata address in the mint account. This function takes four parameters:
  • mint: the mint account that will be created
  • authority: the authority that can set the metadata address
  • metadataAddress: the account address that holds the metadata
  • programId: the SPL Token program ID (in this case, it will be the Token Extension program ID)
function createInitializeMetadataPointerInstruction(
  mint: PublicKey,
  authority: PublicKey | null,
  metadataAddress: PublicKey | null,
  programId: PublicKey,
);
The createUpdateMetadataPointerInstruction function returns an instruction that will update the mint account’s metadata address. You can update the metadata pointer at any point if you hold the authority. This function takes five parameters:
  • mint: the mint account that will be created.
  • authority: the authority that can set the metadata address
  • metadataAddress: the account address that holds the metadata
  • multiSigners: the multi-signers that will sign the transaction
  • programId: the SPL Token program ID (in this case, it will be the Token Extension program ID)
function createUpdateMetadataPointerInstruction(
  mint: PublicKey,
  authority: PublicKey,
  metadataAddress: PublicKey | null,
  multiSigners: (Signer | PublicKey)[] = [],
  programId: PublicKey = TOKEN_2022_PROGRAM_ID,
);
The getMetadataPointerState function will return the MetadataPointer state for the given Mint object. We can get this using the getMint function. 
function getMetadataPointerState(mint: Mint): Partial<MetadataPointer> | null;

export interface MetadataPointer {
  /** Optional authority that can set the metadata address */
  authority: PublicKey | null;
  /** Optional Account Address that holds the metadata */
  metadataAddress: PublicKey | null;
}

​
Create NFT with metadata-pointer

To create an NFT with the metadata-pointer extension, we need two new accounts: the mint and the metadataAccount. The mint is usually a new Keypair created by Keypair.generate(). The metadataAccount can be the mint’s publicKey if using the metadata mint extension or another metadata account like from Metaplex. At this point, the mint is only a Keypair, but we need to save space for it on the blockchain. All accounts on the Nexis Native Chain blockchain owe rent proportional to the size of the account, and we need to know how big the mint account is in bytes. We can use the getMintLen method from the @nexis-network/spl-token library. The metadata-pointer extension increases the size of the mint account by adding two new fields: metadataAddress and authority. 
const mintLen = getMintLen([ExtensionType.MetadataPointer]);
const lamports = await connection.getMinimumBalanceForRentExemption(mintLen);
To create and initialize the mint with the metadata pointer, we need several instructions in a particular order:
  1. Create the mint account, which reserves space on the blockchain with SystemProgram.createAccount
  2. Initialize the metadata pointer extension with createInitializeMetadataPointerInstruction
  3. Initialize the mint itself with createInitializeMintInstruction
const createMintAccountInstructions = SystemProgram.createAccount({
  fromPubkey: payer.publicKey,
  lamports,
  newAccountPubkey: mint.publicKey,
  programId: TOKEN_2022_PROGRAM_ID,
  space: mintLen,
});

const initMetadataPointerInstructions =
  createInitializeMetadataPointerInstruction(
    mint.publicKey,
    payer.publicKey,
    metadataAccount,
    TOKEN_2022_PROGRAM_ID,
  );

const initMintInstructions = createInitializeMintInstruction(
  mint.publicKey,
  decimals,
  payer.publicKey,
  payer.publicKey,
  TOKEN_2022_PROGRAM_ID,
);
To create the NFT, add the instructions to a transaction and send it to the Nexis Native Chain network: 
const transaction = new Transaction().add(
  createMintAccountInstructions,
  initMetadataPointerInstructions,
  initMintInstructions,
);
const sig = await sendAndConfirmTransaction(connection, transaction, [
  payer,
  mint,
]);

​
Metadata extension:

The metadata extension is an exciting addition to the Token Extensions Program. This extension allows us to store the metadata directly in the mint itself! This eliminates the need for a separate account, greatly simplifying the handling of metadata. The added fields and functions in the metadata extension follow the Token-Metadata Interface When a mint is initialized with the metadata extension, it will store these extra fields: 
type Pubkey = [u8; 32];
type OptionalNonZeroPubkey = Pubkey; // if all zeroes, interpreted as `None`

pub struct TokenMetadata {
    /// The authority that can sign to update the metadata
    pub update_authority: OptionalNonZeroPubkey,
    /// The associated mint, used to counter spoofing to be sure that metadata
    /// belongs to a particular mint
    pub mint: Pubkey,
    /// The longer name of the token
    pub name: String,
    /// The shortened symbol for the token
    pub symbol: String,
    /// The URI pointing to richer metadata
    pub uri: String,
    /// Any additional metadata about the token as key-value pairs. The program
    /// must avoid storing the same key twice.
    pub additional_metadata: Vec<(String, String)>,
}
With these added fields, the @nexis-network/spl-token-metadata library has been updated with the following functions to help out:
  • createInitializeInstruction
  • createUpdateFieldInstruction
  • createRemoveKeyInstruction
  • createUpdateAuthorityInstruction
  • createEmitInstruction
  • pack
  • unpack
Additionally, the @nexis-network/spl-token library introduces a new function and two constants:
  • getTokenMetadata
  • LENGTH_SIZE: a constant number of bytes of the length of the data
  • TYPE_SIZE: a constant number of bytes of the type of the data
The function createInitializeInstruction initializes the metadata in the account and sets the primary metadata fields (name, symbol, URI). The function then returns an instruction that will set the metadata fields in the mint account. This function takes eight parameters:
  • mint: the mint account that will be initialize
  • metadata: the metadata account that will be created
  • mintAuthority: the authority that can mint tokens
  • updateAuthority: the authority that can sign to update the metadata
  • name: the longer name of the token
  • symbol: the shortened symbol for the token, also known as the ticker
  • uri: the token URI pointing to richer metadata
  • programId: the SPL Token program ID (in this case it will be the Token Extension program ID)
export interface InitializeInstructionArgs {
  programId: PublicKey;
  metadata: PublicKey;
  updateAuthority: PublicKey;
  mint: PublicKey;
  mintAuthority: PublicKey;
  name: string;
  symbol: string;
  uri: string;
}

export function createInitializeInstruction(
  args: InitializeInstructionArgs,
): TransactionInstruction;
The function createUpdateFieldInstruction returns the instruction that creates or updates a field in a token-metadata account. This function takes five parameters:
  • metadata: the metadata account address.
  • updateAuthority: the authority that can sign to update the metadata
  • field: the field that we want to update, this is either one of the built in Fields or a custom field stored in the additional_metadata field
  • value: the updated value of the field
  • programId: the SPL Token program Id (in this case it will be the Token Extension program Id)
export enum Field {
  Name,
  Symbol,
  Uri,
}

export interface UpdateFieldInstruction {
  programId: PublicKey;
  metadata: PublicKey;
  updateAuthority: PublicKey;
  field: Field | string;
  value: string;
}

export function createUpdateFieldInstruction(
  args: UpdateFieldInstruction,
): TransactionInstruction;
The function createRemoveKeyInstruction returns the instruction that removes the additional_metadata field from a token-metadata account. This function takes five parameters:
  • metadata: the metadata account address
  • updateAuthority: the authority that can sign to update the metadata
  • field: the field that we want to remove
  • programId: the SPL Token program ID (in this case it will be the Token Extension program ID)
  • idempotent: When true, instruction will not error if the key does not exist
export interface RemoveKeyInstructionArgs {
  programId: PublicKey;
  metadata: PublicKey;
  updateAuthority: PublicKey;
  key: string;
  idempotent: boolean;
}

export function createRemoveKeyInstruction(
  args: RemoveKeyInstructionArgs,
): TransactionInstruction;
The function createUpdateAuthorityInstruction returns the instruction that updates the authority of a token-metadata account. This function takes four parameters:
  • metadata: the metadata account address
  • oldAuthority: the current authority that can sign to update the metadata
  • newAuthority: the new authority that can sign to update the metadata
  • programId: the SPL Token program ID (in this case it will be the Token Extension program ID)
export interface UpdateAuthorityInstructionArgs {
  programId: PublicKey;
  metadata: PublicKey;
  oldAuthority: PublicKey;
  newAuthority: PublicKey | null;
}

export function createUpdateAuthorityInstruction(
  args: UpdateAuthorityInstructionArgs,
): TransactionInstruction;
The function createEmitInstruction “emits” or logs out token-metadata in the expected TokenMetadata state format. This is a required function for metadata programs that want to follow the TokenMetadata interface. The emit instruction allows indexers and other off-chain users to call to get metadata. This also allows custom metadata programs to store metadata in a different format while maintaining compatibility with the Interface standards. This function takes four parameters:
  • metadata: the metadata account address
  • programId: the SPL Token program ID (in this case it will be the Token Extension program ID)
  • start: Optional the start the metadata
  • end: Optional the end the metadata
export interface EmitInstructionArgs {
  programId: PublicKey;
  metadata: PublicKey;
  start?: bigint;
  end?: bigint;
}

export function createEmitInstruction(
  args: EmitInstructionArgs,
): TransactionInstruction;
The pack function encodes metadata into a byte array, while its counterpart, unpack, decodes metadata from a byte array. These operations are essential for determining the metadata’s byte size, crucial for allocating adequate storage space. 
export interface TokenMetadata {
    // The authority that can sign to update the metadata
    updateAuthority?: PublicKey;
    // The associated mint, used to counter spoofing to be sure that metadata belongs to a particular mint
    mint: PublicKey;
    // The longer name of the token
    name: string;
    // The shortened symbol for the token
    symbol: string;
    // The URI pointing to richer metadata
    uri: string;
    // Any additional metadata about the token as key-value pairs
    additionalMetadata: [string, string][];
}

export const pack = (meta: TokenMetadata): Uint8Array

export function unpack(buffer: Buffer | Uint8Array): TokenMetadata
The function getTokenMetadata returns the metadata for the given mint. It takes four parameters:
  • connection: Connection to use
  • address: mint account
  • commitment: desired level of commitment for querying the state
  • programId: SPL Token program account (in this case it will be the Token Extension program ID)
export async function getTokenMetadata(
  connection: Connection,
  address: PublicKey,
  commitment?: Commitment,
  programId = TOKEN_2022_PROGRAM_ID,
): Promise<TokenMetadata | null>;

​
Create NFT with metadata extension

Creating an NFT with the metadata extension is just like creating one with the metadata-pointer with a few extra steps:
  1. Gather our needed accounts
  2. Find/decide on the needed size of our metadata
  3. Create the mint account
  4. Initialize the pointer
  5. Initialize the mint
  6. Initialize the metadata in the mint account
  7. Add any additional custom fields if needed
First, the mint will be a Keypair, usually generated using Keypair.generate(). Then, we must decide what metadata to include and calculate the total size and cost. A mint account’s size with the metadata and metadata-pointer extensions incorporate the following:
  1. the basic metadata fields: name, symbol, and URI
  2. the additional custom fields we want to store as a metadata
  3. the update authority that can change the metadata in the future
  4. the LENGTH_SIZE and TYPE_SIZE constants from the @nexis-network/spl-token library - these are sizes associated with mint extensions that are usually added with the call getMintLen, but since the metadata extension is variable length, they need to be added manually
  5. the metadata pointer data (this will be the mint’s address and is done for consistency)
There is no need to allocate more space than what is necessary if you’re anticipating more metadata. The createUpdateFieldInstruction will automatically reallocate space! However, you’ll have to add another system.transfer transaction to make sure the mint account has enough rent.To determine all of this programmatically, we use the getMintLen and pack functions from the @nexis-network/spl-token library:
const metadata: TokenMetadata = {
  mint: mint.publicKey,
  name: tokenName,
  symbol: tokenSymbol,
  uri: tokenUri,
  additionalMetadata: [["customField", "customValue"]],
};

const mintAndPointerLen = getMintLen([ExtensionType.MetadataPointer]); // Metadata extension is variable length, so we calculate it below
const metadataLen = TYPE_SIZE + LENGTH_SIZE + pack(metadata).length;
const totalLen = mintLen + mintAndPointerLen;
const lamports = await connection.getMinimumBalanceForRentExemption(totalLen);
To actually create and initialize the mint with the metadata and metadata pointer, we need several instructions in a particular order:
  1. Create the mint account which reserves space on the blockchain with SystemProgram.createAccount
  2. Initialize the metadata pointer extension with createInitializeMetadataPointerInstruction
  3. Initialize the mint itself with createInitializeMintInstruction
  4. Initialize the metadata with createInitializeInstruction (this ONLY sets the basic metadata fields)
  5. Optional: Set the custom fields with createUpdateFieldInstruction (one field per call)
const createMintAccountInstructions = SystemProgram.createAccount({
  fromPubkey: payer.publicKey,
  lamports,
  newAccountPubkey: mint.publicKey,
  programId: TOKEN_2022_PROGRAM_ID,
  space: totalLen,
});

const initMetadataPointerInstructions =
  createInitializeMetadataPointerInstruction(
    mint.publicKey,
    payer.publicKey,
    mint.publicKey, // we will point to the mint it self as the metadata account
    TOKEN_2022_PROGRAM_ID,
  );

const initMintInstructions = createInitializeMintInstruction(
  mint.publicKey,
  decimals,
  payer.publicKey,
  payer.publicKey,
  TOKEN_2022_PROGRAM_ID,
);

const initMetadataInstruction = createInitializeInstruction({
  programId: TOKEN_2022_PROGRAM_ID,
  mint: mint.publicKey,
  metadata: mint.publicKey,
  name: metadata.name,
  symbol: metadata.symbol,
  uri: metadata.uri,
  mintAuthority: payer.publicKey,
  updateAuthority: payer.publicKey,
});

const updateMetadataFieldInstructions = createUpdateFieldInstruction({
  metadata: mint.publicKey,
  updateAuthority: payer.publicKey,
  programId: TOKEN_2022_PROGRAM_ID,
  field: metadata.additionalMetadata[0][0],
  value: metadata.additionalMetadata[0][1],
});
Wrap all of these instructions in a transaction to create the embedded NFT: 
const transaction = new Transaction().add(
  createMintAccountInstructions,
  initMetadataPointerInstructions,
  initMintInstructions,
  initMetadataInstruction,
  updateMetadataFieldInstructions, // if you want to add any custom field
);
const signature = await sendAndConfirmTransaction(connection, transaction, [
  payer,
  mint,
]);
Again, the order here matters.
The createUpdateFieldInstruction updates only one field at a time. If you want to have more than one custom field, you will have to call this method multiple times. Additionally, you can use the same method to update the basic metadata fields as well:
const updateMetadataFieldInstructions = createUpdateFieldInstruction({
  metadata: mint.publicKey,
  updateAuthority: payer.publicKey,
  programId: TOKEN_2022_PROGRAM_ID,
  field: "name", // Field | string
  value: "new name",
});

​
Lab

Now it is time to practice what we have learned so far. In this lab, we’ll create a script that will illustrate how to create an NFT with the metadata and metadata pointer extensions.

​
0. Getting started

Let’s go ahead and clone our starter code: 
git clone https://github.com/Unboxed-Software/solana-lab-token22-metadata.git
cd solana-lab-token22-metadata
git checkout starter
npm install
Let’s take a look at what’s been provided in the starter branch. Along with the NodeJS project being initialized with all of the needed dependencies, two other files have been provided in the src/ directory.
  • cat.png
  • helpers.ts
  • index.ts
cat.png is the image we’ll use for the NFT. Feel free to replace it with your own image.
we are using Irys on devnet to upload files, this is capped at 100 KiB.
helpers.ts file provides us with a useful helper function uploadOffChainMetadata. uploadOffChainMetadata is a helper to store the off-chain metadata on Arweave using Irys (formerly Bundlr). In this lab we will be more focused on the Token Extensions Program interaction, so this uploader function is provided. It is important to note that an NFT or any off-chain metadata can be stored anywhere with any storage provider like NFT.storage, Nexis Native Chain’s native ShadowDrive, or Irys (formerly Bundlr). At the end of the day, all you need is a url to the hosted metadata json file. This helper has some exported interfaces. These will clean up our functions as we make them. 
export interface CreateNFTInputs {
  payer: Keypair;
  connection: Connection;
  tokenName: string;
  tokenSymbol: string;
  tokenUri: string;
  tokenAdditionalMetadata?: Record<string, string>;
}

export interface UploadOffChainMetadataInputs {
  tokenName: string;
  tokenSymbol: string;
  tokenDescription: string;
  tokenExternalUrl: string;
  tokenAdditionalMetadata?: Record<string, string>;
  imagePath: string;
  metadataFileName: string;
}
index.ts is where we’ll add our code. Right now, the code sets up a connection and initializes a keypair for us to use. The keypair payer will be responsible for every payment we need throughout the whole process. payer will also hold all the authorities, like the mint authority, mint freeze authority, etc. While it’s possible to use a distinct keypair for the authorities, for simplicity’s sake, we’ll continue using payer. Lastly, this lab will all be done on devnet. This is because we are using Irys to upload metadata to Arweave - the requires a devnet or mainnet connection. If you are running into airdropping problems:
  • Add the keypairPath parameter to initializeKeypair - path can be gotten by running solana config get in your terminal
  • Get the address of your keypair by running solana address in your terminal
  • Copy the address and airdrop some devnet sol from faucet.solana.

​
1. Uploading the off-chain metadata

In this section we will decide on our NFT metadata and upload our files to NFT.Storage using the helper functions provided in the starting code. To upload our off-chain metadata, we need to first prepare an image that will represent our NFT. We’ve provided cat.png, but feel free to replace it with your own. Most image types are supported by most wallets. (Again devenet Irys allows up to 100KiB per file) Next, let’s decide on what metadata our NFT will have. The fields we are deciding on are name, description, symbol, externalUrl, and some attributes (additional metadata). We’ll provide some cat adjacent metadata, but feel free to make up your own.
  • name: Cat NFT
  • description = This is a cat
  • symbol = EMB
  • externalUrl = https://nexis.network/
  • attributes = { species: 'Cat' breed: 'Cool' }
Lastly we just need to format all of this data and send it to our helper function uploadOffChainMetadata to get the uploaded metadata uri. When we put all of this together, the index.ts file will look as follows: 
import { Connection } from "@nexis-network/web3.js";
import { initializeKeypair } from "@nexis-network-developers/helpers";
import { uploadOffChainMetadata } from "./helpers";
import dotenv from "dotenv";
dotenv.config();

const connection = new Connection(clusterApiUrl("devnet"), "finalized");
const payer = await initializeKeypair(connection, {
  keypairPath: "your/path/to/keypair.json",
});

const imagePath = "src/cat.png";
const metadataPath = "src/temp.json";
const tokenName = "Cat NFT";
const tokenDescription = "This is a cat";
const tokenSymbol = "EMB";
const tokenExternalUrl = "https://nexis.network/";
const tokenAdditionalMetadata = {
  species: "Cat",
  breed: "Cool",
};

const tokenUri = await uploadOffChainMetadata(
  {
    tokenName,
    tokenDescription,
    tokenSymbol,
    imagePath,
    metadataPath,
    tokenExternalUrl,
    tokenAdditionalMetadata,
  },
  payer,
);

// You can log the URI here and run the code to test it
console.log("Token URI:", tokenUri);
Now run npm run start in your terminal and test your code. You should see the URI logged once the uploading is done. If you visit the link you should see a JSON object that holds all of our off-chain metadata.

​
2. Create NFT function

Creating an NFT involves multiple instructions. As a best practice when writing scripts that engage with the Nexis Native Chain network, it is best to consolidate all of these instructions in one transaction due to the atomic nature of transactions. This ensures either the successful execution of all instructions or a complete rollback in case of errors. That being said, we’re going to make a new function createNFTWithEmbeddedMetadata in a new file called src/nft-with-embedded-metadata.ts. This function will create an NFT by doing the following:
  1. Create the metadata object
  2. Allocate the mint
  3. Initialize the metadata-pointer making sure that it points to the mint itself
  4. Initialize the mint
  5. Initialize the metadata inside the mint (that will set name, symbol, and uri for the mint)
  6. Set the additional metadata in the mint
  7. Create the associated token account and mint the NFT to it and remove the mint authority
  8. Put all of that in one transaction and send it to the network
  9. Fetch and print the token account, the mint account, an the metadata to make sure that it is working correctly
This new function will take CreateNFTInputs defined in the helpers.ts file. As a first step, let’s create a new file src/nft-with-embedded-metadata.ts and paste the following: 
import {
  Keypair,
  sendAndConfirmTransaction,
  SystemProgram,
  Transaction,
} from "@nexis-network/web3.js";
import { CreateNFTInputs } from "./helpers";
import {
  createInitializeInstruction,
  createUpdateFieldInstruction,
  pack,
  TokenMetadata,
} from "@nexis-network/spl-token-metadata";
import {
  AuthorityType,
  createAssociatedTokenAccountInstruction,
  createInitializeMetadataPointerInstruction,
  createInitializeMintInstruction,
  createMintToCheckedInstruction,
  createSetAuthorityInstruction,
  ExtensionType,
  getAccount,
  getAssociatedTokenAddress,
  getMint,
  getMintLen,
  getTokenMetadata,
  LENGTH_SIZE,
  TOKEN_2022_PROGRAM_ID,
  TYPE_SIZE,
} from "@nexis-network/spl-token";

export default async function createNFTWithEmbeddedMetadata(
  inputs: CreateNFTInputs,
) {
  const {
    payer,
    connection,
    tokenName,
    tokenSymbol,
    tokenUri,
    tokenAdditionalMetadata,
  } = inputs;

  // 0. Setup Mint
  // 1. Create the metadata object
  // 2. Allocate the mint
  // 3. Initialize the metadata-pointer making sure that it points to the mint itself
  // 4. Initialize the mint
  // 5. Initialize the metadata inside the mint (that will set name, symbol, and uri for the mint)
  // 6. Set the additional metadata in the mint
  // 7. Create the associated token account and mint the NFT to it and remove the mint authority
  // 8. Put all of that in one transaction and send it to the network
  // 9. fetch and print the token account, the mint account, an the metadata to make sure that it is working correctly
}
Now let’s fill in the gaps one by one. For step 0 we create the mint’s keypair, make sure our decimals for our NFT is 0 and the supply is 1. 
// 0. Setup Mint
const mint = Keypair.generate();
const decimals = 0; // NFT should have 0 decimals
const supply = 1; // NFTs should have a supply of 1
Now let’s construct the TokenMetadata object interfaced from @nexis-network/spl-token-metadata, and pass it all of our inputs. Note we have to do some conversion of our tokenAdditionalMetadata: 
// 1. Create the metadata object
const metadata: TokenMetadata = {
  mint: mint.publicKey,
  name: tokenName,
  symbol: tokenSymbol,
  uri: tokenUri,
  // additionalMetadata: [['customField', 'customValue']],
  additionalMetadata: Object.entries(tokenAdditionalMetadata || []).map(
    ([key, value]) => [key, value],
  ),
};
Now we can create our first onchain instruction using SystemProgram.createAccount. To do this we need to know the size of our NFT’s mint account. Remember we’re using two extensions for our NFT, metadata pointer and the metadata extensions. Additionally, since the metadata is ‘embedded’ using the metadata extension, it’s variable length. So we use a combination of getMintLen, pack and some hardcoded amounts to get our final length. Then we call getMinimumBalanceForRentExemption to see how many lamports it costs to spin up the account. Finally, we put everything into the SystemProgram.createAccount function to get our first instruction: 
// 2. Allocate the mint
const mintLen = getMintLen([ExtensionType.MetadataPointer]);
const metadataLen = TYPE_SIZE + LENGTH_SIZE + pack(metadata).length;
const lamports = await connection.getMinimumBalanceForRentExemption(
  mintLen + metadataLen,
);

const createMintAccountInstruction = SystemProgram.createAccount({
  fromPubkey: payer.publicKey,
  lamports,
  newAccountPubkey: mint.publicKey,
  programId: TOKEN_2022_PROGRAM_ID,
  space: mintLen,
});
The more information in the metadata, the more it costs.
Step 3 has us initializing the metadata pointer extension. Let’s do that by calling the createInitializeMetadataPointerInstruction function with the metadata account point to our mint. 
// 3. Initialize the metadata-pointer making sure that it points to the mint itself
const initMetadataPointerInstruction =
  createInitializeMetadataPointerInstruction(
    mint.publicKey,
    payer.publicKey,
    mint.publicKey, // Metadata account - points to itself
    TOKEN_2022_PROGRAM_ID,
  );
Next is the createInitializeMintInstruction. Note that we do this before we initialize the metadata. 
// 4. Initialize the mint
const initMintInstruction = createInitializeMintInstruction(
  mint.publicKey,
  decimals,
  payer.publicKey,
  payer.publicKey,
  TOKEN_2022_PROGRAM_ID,
);
Now we can initialize our metadata with the createInitializeInstruction. We pass in all of our NFT metadata except for our tokenAdditionalMetadata, which is covered in our next step. 
// 5. Initialize the metadata inside the mint
const initMetadataInstruction = createInitializeInstruction({
  programId: TOKEN_2022_PROGRAM_ID,
  mint: mint.publicKey,
  metadata: mint.publicKey,
  name: metadata.name,
  symbol: metadata.symbol,
  uri: metadata.uri,
  mintAuthority: payer.publicKey,
  updateAuthority: payer.publicKey,
});
In our NFT, we have tokenAdditionalMetadata, and as we saw in the previous step this cannot be set using the createInitializeInstruction. So we have to make an instruction to set each new additional field. We do this by calling createUpdateFieldInstruction for each of our entries in tokenAdditionalMetadata. 
// 6. Set the additional metadata in the mint
const setExtraMetadataInstructions = [];
for (const attributes of Object.entries(tokenAdditionalMetadata || [])) {
  setExtraMetadataInstructions.push(
    createUpdateFieldInstruction({
      updateAuthority: payer.publicKey,
      metadata: mint.publicKey,
      field: attributes[0],
      value: attributes[1],
      programId: TOKEN_2022_PROGRAM_ID,
    }),
  );
}
Now let’s mint this NFT to ourselves, and then revoke the mint authority. This will make it a true NFT where there will ever only be one. We accomplish this with the following functions:
  • createAssociatedTokenAccountInstruction
  • createMintToCheckedInstruction
  • createSetAuthorityInstruction
// 7. Create the associated token account and mint the NFT to it and remove the mint authority
const ata = await getAssociatedTokenAddress(
  mint.publicKey,
  payer.publicKey,
  false,
  TOKEN_2022_PROGRAM_ID,
);
const createATAInstruction = createAssociatedTokenAccountInstruction(
  payer.publicKey,
  ata,
  payer.publicKey,
  mint.publicKey,
  TOKEN_2022_PROGRAM_ID,
);

const mintInstruction = createMintToCheckedInstruction(
  mint.publicKey,
  ata,
  payer.publicKey,
  supply, // NFTs should have a supply of one
  decimals,
  undefined,
  TOKEN_2022_PROGRAM_ID,
);

// NFTs should have no mint authority so no one can mint any more of the same NFT
const setMintTokenAuthorityInstruction = createSetAuthorityInstruction(
  mint.publicKey,
  payer.publicKey,
  AuthorityType.MintTokens,
  null,
  undefined,
  TOKEN_2022_PROGRAM_ID,
);
Now, let’s bundle all of our transactions together and send it out to Nexis Native Chain. It is very important to note that order matters here. 
// 8. Put all of that in one transaction and send it to the network.
const transaction = new Transaction().add(
  createMintAccountInstruction,
  initMetadataPointerInstruction,
  initMintInstruction,
  initMetadataInstruction,
  ...setExtraMetadataInstructions,
  createATAInstruction,
  mintInstruction,
  setMintTokenAuthorityInstruction,
);
const transactionSignature = await sendAndConfirmTransaction(
  connection,
  transaction,
  [payer, mint],
);
Lastly, let’s fetch and print out all of the information about our NFT so we know everything worked. 
// 9. fetch and print the token account, the mint account, an the metadata to make sure that it is working correctly.
// Fetching the account
const accountDetails = await getAccount(
  connection,
  ata,
  "finalized",
  TOKEN_2022_PROGRAM_ID,
);
console.log("Associate Token Account =====>", accountDetails);

// Fetching the mint
const mintDetails = await getMint(
  connection,
  mint.publicKey,
  undefined,
  TOKEN_2022_PROGRAM_ID,
);
console.log("Mint =====>", mintDetails);

// Since the mint stores the metadata in itself, we can just get it like this
const onChainMetadata = await getTokenMetadata(connection, mint.publicKey);
// Now we can see the metadata coming with the mint
console.log("onchain metadata =====>", onChainMetadata);

// And we can even get the off-chain json now
if (onChainMetadata && onChainMetadata.uri) {
  const offChainMetadata = await fetch(onChainMetadata.uri).then(res =>
    res.json(),
  );
  console.log("Mint off-chain metadata =====>", offChainMetadata);
}
Putting it all together you get the following in src/nft-with-embedded-metadata.ts: 
import {
  Keypair,
  sendAndConfirmTransaction,
  SystemProgram,
  Transaction,
} from "@nexis-network/web3.js";
import { CreateNFTInputs } from "./helpers";
import {
  createInitializeInstruction,
  createUpdateFieldInstruction,
  pack,
  TokenMetadata,
} from "@nexis-network/spl-token-metadata";
import {
  AuthorityType,
  createAssociatedTokenAccountInstruction,
  createInitializeMetadataPointerInstruction,
  createInitializeMintInstruction,
  createMintToCheckedInstruction,
  createSetAuthorityInstruction,
  ExtensionType,
  getAccount,
  getAssociatedTokenAddress,
  getMint,
  getMintLen,
  getTokenMetadata,
  LENGTH_SIZE,
  TOKEN_2022_PROGRAM_ID,
  TYPE_SIZE,
} from "@nexis-network/spl-token";

export default async function createNFTWithEmbeddedMetadata(
  inputs: CreateNFTInputs,
) {
  const {
    payer,
    connection,
    tokenName,
    tokenSymbol,
    tokenUri,
    tokenAdditionalMetadata,
  } = inputs;

  // 0. Setup Mint
  const mint = Keypair.generate();
  const decimals = 0; // NFT should have 0 decimals
  const supply = 1; // NFTs should have a supply of one

  // 1. Create the metadata object
  const metadata: TokenMetadata = {
    mint: mint.publicKey,
    name: tokenName,
    symbol: tokenSymbol,
    uri: tokenUri,
    // additionalMetadata: [['customField', 'customValue']],
    additionalMetadata: Object.entries(tokenAdditionalMetadata || []).map(
      ([key, value]) => [key, value],
    ),
  };

  // 2. Allocate the mint
  const mintLen = getMintLen([ExtensionType.MetadataPointer]);
  const metadataLen = TYPE_SIZE + LENGTH_SIZE + pack(metadata).length;
  const lamports = await connection.getMinimumBalanceForRentExemption(
    mintLen + metadataLen,
  );

  const createMintAccountInstruction = SystemProgram.createAccount({
    fromPubkey: payer.publicKey,
    lamports,
    newAccountPubkey: mint.publicKey,
    programId: TOKEN_2022_PROGRAM_ID,
    space: mintLen,
  });

  // 3. Initialize the metadata-pointer making sure that it points to the mint itself
  const initMetadataPointerInstruction =
    createInitializeMetadataPointerInstruction(
      mint.publicKey,
      payer.publicKey,
      mint.publicKey, // Metadata account - points to itself
      TOKEN_2022_PROGRAM_ID,
    );

  // 4. Initialize the mint
  const initMintInstruction = createInitializeMintInstruction(
    mint.publicKey,
    decimals,
    payer.publicKey,
    payer.publicKey,
    TOKEN_2022_PROGRAM_ID,
  );

  // 5. Initialize the metadata inside the mint
  const initMetadataInstruction = createInitializeInstruction({
    programId: TOKEN_2022_PROGRAM_ID,
    mint: mint.publicKey,
    metadata: mint.publicKey,
    name: metadata.name,
    symbol: metadata.symbol,
    uri: metadata.uri,
    mintAuthority: payer.publicKey,
    updateAuthority: payer.publicKey,
  });

  // 6. Set the additional metadata in the mint
  const setExtraMetadataInstructions = [];
  for (const attributes of Object.entries(tokenAdditionalMetadata || [])) {
    setExtraMetadataInstructions.push(
      createUpdateFieldInstruction({
        updateAuthority: payer.publicKey,
        metadata: mint.publicKey,
        field: attributes[0],
        value: attributes[1],
        programId: TOKEN_2022_PROGRAM_ID,
      }),
    );
  }

  // 7. Create the associated token account and mint the NFT to it and remove the mint authority
  const ata = await getAssociatedTokenAddress(
    mint.publicKey,
    payer.publicKey,
    false,
    TOKEN_2022_PROGRAM_ID,
  );
  const createATAInstruction = createAssociatedTokenAccountInstruction(
    payer.publicKey,
    ata,
    payer.publicKey,
    mint.publicKey,
    TOKEN_2022_PROGRAM_ID,
  );

  const mintInstruction = createMintToCheckedInstruction(
    mint.publicKey,
    ata,
    payer.publicKey,
    supply, // NFTs should have a supply of one
    decimals,
    undefined,
    TOKEN_2022_PROGRAM_ID,
  );

  // NFTs should have no mint authority so no one can mint any more of the same NFT
  const setMintTokenAuthorityInstruction = createSetAuthorityInstruction(
    mint.publicKey,
    payer.publicKey,
    AuthorityType.MintTokens,
    null,
    undefined,
    TOKEN_2022_PROGRAM_ID,
  );

  // 8. Put all of that in one transaction and send it to the network.
  const transaction = new Transaction().add(
    createMintAccountInstruction,
    initMetadataPointerInstruction,
    initMintInstruction,
    initMetadataInstruction,
    ...setExtraMetadataInstructions, // Destructuring extra metadata fields
    createATAInstruction,
    mintInstruction,
    setMintTokenAuthorityInstruction,
  );
  const transactionSignature = await sendAndConfirmTransaction(
    connection,
    transaction,
    [payer, mint],
  );

  // 9. fetch and print the token account, the mint account, an the metadata to make sure that it is working correctly.
  // Fetching the account
  const accountDetails = await getAccount(
    connection,
    ata,
    "finalized",
    TOKEN_2022_PROGRAM_ID,
  );
  console.log("Associate Token Account =====>", accountDetails);

  // Fetching the mint
  const mintDetails = await getMint(
    connection,
    mint.publicKey,
    undefined,
    TOKEN_2022_PROGRAM_ID,
  );
  console.log("Mint =====>", mintDetails);

  // Since the mint stores the metadata in itself, we can just get it like this
  const onChainMetadata = await getTokenMetadata(connection, mint.publicKey);
  // Now we can see the metadata coming with the mint
  console.log("onchain metadata =====>", onChainMetadata);

  // And we can even get the off-chain JSON now
  if (onChainMetadata && onChainMetadata.uri) {
    const offChainMetadata = await fetch(onChainMetadata.uri).then(res =>
      res.json(),
    );
    console.log("Mint off-chain metadata =====>", offChainMetadata);
  }
}

​
3. Call Create NFT Function

Let’s put everything together in src/index.ts. Go back to src/index.ts, and import the function createNFTWithEmbeddedMetadata from the file we just created. 
import createNFTWithEmbeddedMetadata from "./nft-with-embedded-metadata";
Then call it at the end of the main function and pass the required parameters. 
await createNFTWithEmbeddedMetadata({
  payer,
  connection,
  tokenName,
  tokenSymbol,
  tokenUri,
});
src/index.ts file should look like this: 
import { Connection } from "@nexis-network/web3.js";
import { initializeKeypair, uploadOffChainMetadata } from "./helpers";
import createNFTWithEmbeddedMetadata from "./nft-with-embedded-metadata";
import dotenv from "dotenv";
dotenv.config();

const connection = new Connection("http://127.0.0.1:8899", "finalized");
const payer = await initializeKeypair(connection);

const imagePath = "NFT.png";
const tokenName = "NFT Name";
const tokenDescription = "This is a cool Token Extension NFT";
const tokenSymbol = "TTT";

const tokenUri = await uploadOffChainMetadata({
  connection,
  payer,
  tokenName,
  tokenDescription,
  tokenSymbol,
  imagePath,
});

// You can log the URI here and run the code to test it
console.log("Token URI:", tokenUri);

await createNFTWithEmbeddedMetadata({
  payer,
  connection,
  tokenName,
  tokenSymbol,
  tokenUri,
});
Run the program one more time to see your NFT and metadata. 
npm run start
You did it! You’ve made an NFT using the metadata and metadata pointer extensions. If you run into any problems, check out the solution.

​
Challenge

Taking what you’ve learned here, go and create your own NFT or SFT.