Mesh SDK Transaction Skill

AI-assisted Cardano transaction building using MeshTxBuilder from @meshsdk/transaction.

Package Info

npm install @meshsdk/transaction
# or
npm install @meshsdk/core  # includes transaction + wallet + provider

Quick Reference

Constructor Options

import { MeshTxBuilder } from '@meshsdk/transaction';

const txBuilder = new MeshTxBuilder({
  fetcher?: IFetcher,      // For querying UTxOs (e.g., BlockfrostProvider)
  submitter?: ISubmitter,  // For submitting transactions
  evaluator?: IEvaluator,  // For script execution cost estimation
  serializer?: IMeshTxSerializer,  // Custom serializer
  selector?: IInputSelector,       // Custom coin selection
  isHydra?: boolean,       // Hydra L2 mode (zero fees)
  params?: Partial<Protocol>,  // Custom protocol parameters
  verbose?: boolean,       // Enable logging
});

Completion Methods

Files

• [TRANSACTION.md](./TRANSACTION.md) - Complete API reference
• [PATTERNS.md](./PATTERNS.md) - Common transaction recipes
• [AIKEN-MAPPING.md](./AIKEN-MAPPING.md) - Aiken smart contract type → MeshTxBuilder mapping
• [TROUBLESHOOTING.md](./TROUBLESHOOTING.md) - Error solutions

Key Concepts

Fluent API

All methods return this for chaining:

txBuilder
  .txIn(hash, index)
  .txOut(address, amount)
  .changeAddress(addr)
  .complete();

Script Versions

Choose the version matching the script's Plutus version:

LanguageVersion type = "V1" | "V2" | "V3"

Each script context has two equivalent calling styles — static shortcuts and dynamic version:

Default to V3 for new Conway-era scripts. Only use V2/V1 for scripts compiled against those specific Plutus versions.

Data Types (Datum & Redeemer Formats)

Datum and redeemer values accept three formats via the type parameter:

"Mesh" (default) — Use alternative, NOT constructor:

import { mConStr0, mConStr1 } from '@meshsdk/common';

// Mesh Data type uses "alternative" for ConstrPlutusData
const datum = { alternative: 0, fields: [42, "deadbeef"] };
// Or use helper: mConStr0([42, "deadbeef"])
// mConStr1([...]) for constructor index 1, etc.

.txOutInlineDatumValue(datum)           // default type is "Mesh"
.txOutInlineDatumValue(datum, "Mesh")   // explicit

"JSON" — Cardano-CLI format, uses constructor:

import { conStr0, integer, byteString, pubKeyAddress } from '@meshsdk/common';

// JSON format uses "constructor" with typed field wrappers
const datum = conStr0([integer(42), byteString("deadbeef")]);
// Equivalent to: { constructor: 0, fields: [{ int: 42 }, { bytes: "deadbeef" }] }

.txOutInlineDatumValue(datum, "JSON")   // MUST specify "JSON"

"CBOR" — Pre-serialized hex:

.txOutInlineDatumValue("d8799f182aff", "CBOR")

Convention from real MeshJS contracts:

Note: Some contracts use Mesh format (mConStr0) for simple datums without a type parameter. Both formats work — the critical rule is matching the type parameter to the format.

See [AIKEN-MAPPING.md](./AIKEN-MAPPING.md) for complete Aiken type → Mesh data mapping.

CRITICAL: If you omit the type parameter, the default is "Mesh". Using { constructor: 0, ... } without specifying "JSON" will cause errors.

Reference Scripts

Use *TxInReference() methods to reference scripts stored on-chain instead of including them in the transaction (reduces tx size/fees).

Important Notes

1. Change address required - complete() fails without changeAddress()
2. Collateral required - Script transactions need txInCollateral()
3. Order matters - Call spendingPlutusScriptV3() BEFORE txIn() for script inputs
4. Coin selection - Provide UTxOs via selectUtxosFrom() for auto-selection
5. Datum format - Default "Mesh" type uses { alternative: 0 }, NOT { constructor: 0 }. Use "JSON" type for { constructor: 0 } (cardano-cli format)
6. Script version - Default to V3 for Conway-era scripts. Match the Plutus version the script was compiled with