Agent Skills: meshjs-cardano

meshjs-cardano

When to use

• Building Cardano dApps with MeshJS (TypeScript/JavaScript)
• Integrating CIP-30 wallet connectors
• Transaction building in browser or Node.js

Operating rules (must follow)

• Confirm MeshJS version and environment (Next.js, Vite, Node)
• Never request seed phrases or private keys
• Handle wallet disconnects gracefully
• Test on preprod before mainnet

Setup

Installation

npm install @meshsdk/core @meshsdk/react
# or
yarn add @meshsdk/core @meshsdk/react

Provider setup

import { BlockfrostProvider } from '@meshsdk/core';

const provider = new BlockfrostProvider('<PROJECT_ID>');
// or for preprod:
const provider = new BlockfrostProvider('<PROJECT_ID>', 'preprod');

Wallet connection (React)

import { CardanoWallet, useWallet } from '@meshsdk/react';

function App() {
  const { connected, wallet } = useWallet();

  return (
    <div>
      <CardanoWallet />
      {connected && <p>Connected!</p>}
    </div>
  );
}

Transaction building

Simple ADA transfer

import { Transaction } from '@meshsdk/core';

const tx = new Transaction({ initiator: wallet })
  .sendLovelace(
    'addr_test1qz...',
    '5000000'  // 5 ADA
  );

const unsignedTx = await tx.build();
const signedTx = await wallet.signTx(unsignedTx);
const txHash = await wallet.submitTx(signedTx);

With native tokens

const tx = new Transaction({ initiator: wallet })
  .sendAssets(
    'addr_test1qz...',
    [
      { unit: 'lovelace', quantity: '2000000' },
      { unit: '<policy_id><asset_name_hex>', quantity: '1' }
    ]
  );

With metadata

const tx = new Transaction({ initiator: wallet })
  .sendLovelace('addr_test1qz...', '1000000')
  .setMetadata(674, { msg: ['Hello from MeshJS'] });

Script interactions

Lock funds at script

import { Data } from '@meshsdk/core';

const datum: Data = {
  alternative: 0,
  fields: [wallet.getPaymentAddress()]
};

const tx = new Transaction({ initiator: wallet })
  .sendLovelace(
    {
      address: scriptAddress,
      datum: { inline: datum }
    },
    '5000000'
  );

Spend from script

const tx = new Transaction({ initiator: wallet })
  .redeemValue({
    value: scriptUtxo,
    script: plutusScript,
    datum: datum,
    redeemer: { data: { alternative: 0, fields: [] } }
  })
  .sendLovelace(recipientAddress, '4500000')
  .setCollateral([collateralUtxo]);

Examples

Example: NFT minting

User request: "Mint an NFT with MeshJS"

Response:

import { ForgeScript, Transaction } from '@meshsdk/core';

// Create minting script (time-locked)
const { pubKeyHash } = wallet.getPaymentAddress();
const forgingScript = ForgeScript.withOneSignature(pubKeyHash);

const assetMetadata = {
  name: 'My NFT',
  image: 'ipfs://...',
  mediaType: 'image/png'
};

const tx = new Transaction({ initiator: wallet })
  .mintAsset(
    forgingScript,
    {
      assetName: 'MyNFT',
      assetQuantity: '1',
      metadata: assetMetadata,
      label: '721',
      recipient: wallet.getPaymentAddress()
    }
  );

const unsignedTx = await tx.build();
const signedTx = await wallet.signTx(unsignedTx);
const txHash = await wallet.submitTx(signedTx);
console.log('Minted:', txHash);

Example: Query UTxOs

import { BlockfrostProvider } from '@meshsdk/core';

const provider = new BlockfrostProvider('<PROJECT_ID>');

// Get UTxOs for address
const utxos = await provider.fetchAddressUTxOs(address);

// Get UTxOs at script address
const scriptUtxos = await provider.fetchAddressUTxOs(scriptAddress);

// Filter by asset
const nftUtxos = utxos.filter(utxo =>
  utxo.output.amount.some(a => a.unit.includes(policyId))
);

Common patterns

Error handling

try {
  const txHash = await wallet.submitTx(signedTx);
  console.log('Success:', txHash);
} catch (error) {
  if (error.message.includes('UTxO')) {
    console.log('UTxO issue - refresh and retry');
  } else if (error.message.includes('collateral')) {
    console.log('Need ADA-only UTxO for collateral');
  }
}

Wallet state management

const { connected, connecting, disconnect, wallet, name } = useWallet();

// Check connection before operations
if (!connected) {
  throw new Error('Wallet not connected');
}

// Get network
const network = await wallet.getNetworkId();
// 0 = testnet, 1 = mainnet

Safety / key handling

• Never request seed phrases
• Validate CIP-30 API availability
• Handle disconnects gracefully
• Show confirmation before signing

References

• shared/PRINCIPLES.md
• MeshJS documentation
• CIP-30 Wallet API