Asset Metadata

Transaction metadata lets you attach arbitrary data to transactions without affecting their execution. Evolution SDK supports attaching metadata through the attachMetadata operation, following Cardano CIP standards.

Common Metadata Labels

Label	CIP	Purpose
674n	CIP-20	Transaction messages/comments
721n	CIP-25	NFT metadata
777n	CIP-27	Royalty information

Attach a Message (CIP-20)

import { Address, Assets, TransactionMetadatum, preprod, Client } from "@evolution-sdk/evolution"

const client = Client.make(preprod)
  .withBlockfrost({
    baseUrl: "https://cardano-preprod.blockfrost.io/api/v0",
    projectId: process.env.BLOCKFROST_API_KEY!
  })
  .withSeed({ mnemonic: process.env.WALLET_MNEMONIC!, accountIndex: 0 })

declare const messageMetadata: TransactionMetadatum.TransactionMetadatum

const tx = await client
  .newTx()
  .payToAddress({
    address: Address.fromBech32("addr_test1vrm9x2dgvdau8vckj4duc89m638t8djmluqw5pdrFollw8qd9k63"),
    assets: Assets.fromLovelace(2_000_000n)
  })
  .attachMetadata({
    label: 674n,
    metadata: messageMetadata
  })
  .build()

const signed = await tx.sign()
await signed.submit()

Multiple Metadata Entries

Chain multiple attachMetadata calls for different labels:

import { Address, Assets, TransactionMetadatum, preprod, Client } from "@evolution-sdk/evolution"

const client = Client.make(preprod)
  .withBlockfrost({
    baseUrl: "https://cardano-preprod.blockfrost.io/api/v0",
    projectId: process.env.BLOCKFROST_API_KEY!
  })
  .withSeed({ mnemonic: process.env.WALLET_MNEMONIC!, accountIndex: 0 })

declare const messageMetadata: TransactionMetadatum.TransactionMetadatum
declare const nftMetadata: TransactionMetadatum.TransactionMetadatum

const tx = await client
  .newTx()
  .payToAddress({
    address: Address.fromBech32("addr_test1vrm9x2dgvdau8vckj4duc89m638t8djmluqw5pdrFollw8qd9k63"),
    assets: Assets.fromLovelace(2_000_000n)
  })
  .attachMetadata({ label: 674n, metadata: messageMetadata })
  .attachMetadata({ label: 721n, metadata: nftMetadata })
  .build()

Next Steps

• Assets Overview — Working with native assets
• Encoding — Data encoding formats