MoltyDEX SDK

x402 auto-pay agent and API client for Solana token swaps. Zero fees, best prices via Jupiter.

Features

• Automatic 402 Handling — Intercepts and processes x402 payment requirements
• Token Swapping — Automatically swaps to required tokens via Jupiter aggregator
• Pluggable Wallet Architecture — Bring your own signer: local keys, MPC wallets, hardware wallets, or custodial
• HTTP Interceptor — Drop-in fetch wrapper that handles payments transparently
• TypeScript — Fully typed with exported TransactionSigner interface

Installation

npm install moltydex

Quick Start

Option 1: Local Wallet (simplest)

import { HTTPInterceptor } from 'moltydex';

const interceptor = new HTTPInterceptor({
  apiUrl: 'https://api.moltydex.com',
  walletPath: '~/.config/solana/id.json',
  autoSwap: true,
});

// All fetch calls now handle 402 responses automatically
const response = await fetch('https://premium-api.com/data');

Option 2: Bring Your Own Signer (MPC, hardware, custodial)

import { X402AutoPayAgent, TransactionSigner } from 'moltydex';

// Implement the TransactionSigner interface with any wallet backend
const mySigner: TransactionSigner = {
  getAddress: () => '7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU',
  signTransaction: async (txBase64: string) => {
    // Sign with your MPC provider, hardware wallet, etc.
    return signedTxBase64;
  },
};

const agent = new X402AutoPayAgent({
  apiUrl: 'https://api.moltydex.com',
  signer: mySigner,
});

const result = await agent.handle402(paymentResponse);

TransactionSigner Interface

The TransactionSigner interface is the core abstraction that makes MoltyDEX wallet-agnostic. Any wallet backend can implement it:

interface TransactionSigner {
  /** Returns the wallet's public key as a base58 string. */
  getAddress(): string;

  /** Signs a base64-encoded Solana transaction, returns signed base64. */
  signTransaction(transactionBase64: string): Promise<string>;

  /** Optional: builds a payment transaction (SOL or SPL token). */
  buildPaymentTransaction?(
    recipientAddress: string,
    tokenMint: string,
    amount: string,
  ): Promise<string>;
}

Built-in implementations:

• WalletManager — loads a local Solana keypair from file or secret key

You can implement it for:

• Turnkey MPC wallets
• Crossmint custodial wallets
• Privy embedded wallets
• Lit Protocol distributed keys
• Hardware wallets (Ledger)
• Any custom signing logic

Configuration

interface AgentConfig {
  apiUrl: string;                   // MoltyDEX API URL

  // Option A: Provide a TransactionSigner (for custom/MPC wallets)
  signer?: TransactionSigner;

  // Option B: Let WalletManager create one (backwards-compatible)
  walletPath?: string;              // Path to wallet JSON file
  walletSecretKey?: Uint8Array | number[] | string;
  walletAddress?: string;           // Optional: for verification

  preferredInputToken?: string;     // Token to swap from (default: SOL)
  autoSwap?: boolean;               // Auto-execute swaps (default: true)
  webhookUrl?: string;              // Optional webhook for status updates
  rpcUrl?: string;                  // Optional: override Solana RPC URL
  maxRetries?: number;              // Max retry attempts (default: 3)
  retryDelay?: number;              // Delay between retries in ms (default: 2000)
}

How It Works

1. Agent makes API call
   ↓
2. API returns 402 Payment Required
   ↓
3. Auto-Pay Agent intercepts
   ↓
4. Parse payment requirements
   ↓
5. Check balance
   ↓
6. Swap tokens if needed (via Jupiter)
   ↓
7. Sign payment with TransactionSigner
   ↓
8. Wait for confirmation
   ↓
9. Retry original request
   ↓
10. Success!

API Reference

Classes

| Class | Description | |-------|-------------| | X402AutoPayAgent | Main agent — accepts AgentConfig with either signer or key material | | HTTPInterceptor | Drop-in fetch wrapper that auto-handles 402 responses | | MoltyDEXClient | Low-level API client for quotes, swaps, balances | | WalletManager | Built-in TransactionSigner implementation using local Solana keypairs |

Types

| Type | Description | |------|-------------| | TransactionSigner | Interface for pluggable wallet backends | | AgentConfig | Configuration for agent/interceptor | | PaymentRequirement | Parsed 402 payment requirement | | AutoPayResult | Result of a payment attempt |

Python SDK

Also available on PyPI:

pip install moltydex

See pypi.org/project/moltydex for Python documentation.

License

MIT — see LICENSE

Links

• Website
• API Docs
• Developer Guide
• npm
• PyPI
• GitHub