polymerdao/polymer-pay-x402engine-chain

x402engine Chain

x402engine provides pay-per-call blockchain operations. Covers wallet analytics, ENS resolution, token metadata, and transaction simulation. No API key needed — payment is handled automatically by the Polymer Pay proxy.

Authentication

All requests route through the Polymer Pay proxy. Include your Polymer Pay API key in every request:

{
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  }
}

Base URL: https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app

To get an Polymer Pay API key, sign up at https://my.pay.polymerlabs.org/dashboard/api-keys.

Common Operations

Wallet Balances

Get token balances for a wallet address across supported chains.

Pricing: $0.005

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/wallet/balances",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
    "chain": "ethereum"
  }
}

Response: JSON with token balances, USD values, and total portfolio value.

Wallet Transactions

Get recent transaction history for a wallet address.

Pricing: $0.005

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/wallet/transactions",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
    "chain": "ethereum"
  }
}

Response: JSON array of recent transactions with hash, from, to, value, and timestamp.

Wallet PnL

Get profit and loss analysis for a wallet.

Pricing: $0.01

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/wallet/pnl",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"
  }
}

Response: JSON with realized/unrealized PnL breakdown per token.

ENS Resolve

Resolve an ENS name to an Ethereum address.

Pricing: $0.001

{
  "method": "GET",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/ens/resolve",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "query": {
    "name": "vitalik.eth"
  }
}

Response: JSON with the resolved Ethereum address.

ENS Reverse

Reverse resolve an Ethereum address to its ENS name.

Pricing: $0.001

{
  "method": "GET",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/ens/reverse",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "query": {
    "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045"
  }
}

Response: JSON with the ENS name associated with the address.

Token Prices (Batch)

Get current prices for multiple tokens.

Pricing: $0.005

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/token/prices",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "tokens": ["bitcoin", "ethereum", "solana"]
  }
}

Response: JSON with current prices for each requested token. Supports up to 200 tokens per request.

Transaction Simulate

Simulate a transaction before sending to preview the outcome.

Pricing: $0.01

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402-gateway-production.up.railway.app/api/tx/simulate",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "from": "0x...",
    "to": "0x...",
    "value": "1000000000000000000",
    "data": "0x...",
    "chain": "ethereum"
  }
}

Response: JSON with simulation results including gas estimate, state changes, and potential errors.

When to Use

• Wallet balances — User asks for a wallet's token balances or holdings
• Transaction history — User asks for a wallet's transaction history
• PnL analysis — User wants to check wallet PnL (profit and loss)
• ENS resolution — User wants to resolve an ENS name to an address (or reverse)
• Token prices — User asks for token prices or metadata
• Transaction simulation — User wants to simulate a transaction before sending
• Crypto prices — User asks about crypto prices, trending coins, or market search

Best Practices

• Supported chains — Wallet endpoints accept EVM addresses and support multiple chains (ethereum, base, polygon, arbitrum, etc.)
• ENS is Ethereum-specific — ENS endpoints work only with Ethereum
• Token limit — The token prices endpoint supports up to 200 tokens per request
• For errors — See @skills/polymer-pay-api-errors/SKILL.md for complete error code reference and troubleshooting