# x402engine
> Pay-per-call API gateway for AI agents. 82 tools, sub-cent pricing, instant crypto payments.

## What is this?
x402engine is an API gateway that provides 82 pay-per-call tools for AI agents using the HTTP 402 payment protocol. Every API call costs between $0.001 and $0.12, paid instantly with stablecoins (USDC on Base, USDC on Solana, or USDm on MegaETH).

## How to connect
- MCP server (recommended): `npx -y x402engine-mcp`
- Remote MCP endpoint: https://x402engine.app/mcp
- REST API base: https://x402-gateway-production.up.railway.app
- Discovery: https://x402-gateway-production.up.railway.app/.well-known/x402.json

## Agent cold start
- Fetch `/.well-known/x402.json` first and use its `baseUrl` for API calls.
- Optionally read `/api/services` or `/llms.txt` to pick a route.
- Call the route without payment to receive `402 Payment Required`.
- Read the `PAYMENT-REQUIRED` header, create one accepted payment proof, and retry with `X-PAYMENT`.
- On success, read the JSON response and optional `PAYMENT-RESPONSE` settlement header.

## Available tools

### Image Generation
- generate_image (fast): $0.015 — AI image generation, fast mode
- generate_image (quality): $0.05 — AI image generation, quality mode
- generate_image (text): $0.12 — AI image with embedded text
- face_swap: $0.08 — identity-preserving face swap via FLUX PuLID; requires `reference_image_url`
- generate_image (nano-banana): $0.10 — Google's Nano Banana 2, fast high-quality with aspect ratio control

### Code Execution
- execute_code: $0.005 — Sandboxed code execution (Python, JS, Bash, R, Ruby, Go, Rust)

### Audio
- transcribe_audio: $0.10 — Audio transcription (Deepgram Nova-3)
- text_to_speech (OpenAI): $0.01 — Text-to-speech via OpenAI
- text_to_speech (ElevenLabs): $0.02 — Text-to-speech via ElevenLabs
- voice_clone_tts (Lux): $0.02 — Voice-cloning TTS at 48kHz; requires `audio_url` reference clip

### LLM Inference (50 models)
- GPT-5.4: $0.10 | GPT-5.4 Pro: $0.30 | GPT-5.3 Codex: $0.08
- GPT-5.2 Pro: $0.25 | GPT-5.2: $0.08 | GPT-5.2 Codex: $0.06 | GPT-5.1: $0.035 | GPT-5 Nano: $0.002
- GPT-4o: $0.04 | GPT-4o Mini: $0.003 | o1: $0.03 | o4-mini: $0.03
- Claude Opus 4.7: $0.09 | Claude Opus 4.6: $0.09 | Claude Opus 4.5: $0.09 | Claude Sonnet 4.6: $0.06 | Claude Sonnet 4.5: $0.06 | Claude Haiku 4.5: $0.02
- Gemini 3.1 Pro: $0.05 | Gemini 3.1 Flash Lite: $0.003 | Gemini 3 Pro: $0.045 | Gemini 3 Flash: $0.012 | Gemini 2.5 Pro: $0.035 | Gemini 2.5 Flash: $0.009 | Gemma 4 31B: $0.003
- DeepSeek V3.2 Speciale: $0.008 | DeepSeek V3.2: $0.005 | DeepSeek V3: $0.005 | DeepSeek R1: $0.01
- Grok 4.20: $0.06 | Grok 4: $0.06 | Grok 4 Fast: $0.004 | Grok Code Fast: $0.04
- Qwen 3.6 Plus: $0.008 | Qwen 3.5: $0.006 | Qwen3 235B: $0.004 | Qwen3 Coder: $0.004
- Llama 4 Maverick: $0.003 | Llama 3.3 70B: $0.002
- Mistral Large 3: $0.006 | Devstral 2: $0.02 | Perplexity Sonar Pro: $0.06 | Cohere Command A: $0.04
- Kimi K2.6: $0.03 | Kimi K2.5: $0.03 | MiniMax M2.7: $0.01 | MiniMax M2.5: $0.01 | GLM-5.1: $0.03 | GLM-5: $0.03 | Seed 1.6: $0.02
- Text Embeddings: $0.001

### Crypto & Market Data
- get_crypto_price: $0.001 — Real-time crypto prices
- get_crypto_markets: $0.002 — Top coins by market cap
- get_crypto_history: $0.003 — Historical price charts
- get_trending_crypto: $0.001 — Trending coins
- search_crypto: $0.001 — Search for coins

### Blockchain & Wallet Analytics
- get_wallet_balances: $0.005 — Token balances for any wallet
- get_wallet_transactions: $0.005 — Transaction history
- get_wallet_pnl: $0.01 — Realized & unrealized profit/loss per token
- get_token_prices: $0.005 — DEX-derived token prices
- get_token_metadata: $0.002 — Token metadata

### ENS
- resolve_ens: $0.001 — ENS name to address
- reverse_ens: $0.001 — Address to ENS name

### IPFS Storage
- pin_to_ipfs: $0.01 — Pin JSON to IPFS
- get_from_ipfs: $0.001 — Retrieve content from IPFS

### Web
- web_scrape: $0.005 — Scrape and extract web page content
- web_screenshot: $0.01 — Capture web page screenshot
- web_search: $0.01 — Neural web search with highlighted snippets (Exa)
- web_content_fetch: $0.005 — Fetch full text content from up to 10 URLs (Exa)

### Travel
- search_flights: $0.02 — Search flights via Google Flights (best flights, prices, airlines, price insights)
- search_hotels: $0.02 — Search hotels via Google Hotels (properties, ratings, amenities, prices)

### Transaction
- simulate_transaction: $0.01 — Simulate EVM transactions

## Payment
All payments use the x402 HTTP payment protocol. When you call an endpoint without payment, it returns HTTP 402 with payment requirements in the response header. Pay with:
- USDC on Base (EVM, ~2s confirmation) — uses @x402/evm SDK, automatic Permit2 signatures
- USDC on Solana (~400ms confirmation) — uses @x402/svm SDK, automatic
- USDm on MegaETH (EVM, ~10ms confirmation) — requires custom scheme (see below)

### Base payment (recommended, simplest)
**Important:** You must use `registerExactEvmScheme` from `@x402/evm/exact/client` — this produces a Permit2 signature that the facilitator verifies. Sending a raw ERC-20 transfer tx hash will NOT work.
```js
import { wrapFetchWithPayment, x402Client } from '@x402/fetch';
import { registerExactEvmScheme } from '@x402/evm/exact/client';
import { privateKeyToAccount } from 'viem/accounts';

const account = privateKeyToAccount(PRIVATE_KEY);
const client = new x402Client();
registerExactEvmScheme(client, { signer: account, networks: ['eip155:8453'] });
const paidFetch = wrapFetchWithPayment(fetch, client, {
  paymentRequirementsSelector: (accepts) => accepts.find(a => a.network === 'eip155:8453'),
});

const res = await paidFetch('https://x402-gateway-production.up.railway.app/api/crypto/price?ids=bitcoin');
```

### Solana payment
```js
import { x402Client, wrapFetchWithPayment } from '@x402/fetch';
import { ExactSvmScheme } from '@x402/svm'; // v2.2.0
import { createKeyPairSignerFromBytes } from '@solana/kit';

const signer = await createKeyPairSignerFromBytes(keypairBytes);
const scheme = new ExactSvmScheme(signer);
const client = new x402Client().register('solana:*', scheme);
const paidFetch = wrapFetchWithPayment(fetch, client);
```

### MegaETH payment (~10ms, cheapest gas)
The @x402/evm SDK doesn't support MegaETH natively. Use this custom scheme with `wrapFetchWithPaymentFromConfig`:
```js
import { wrapFetchWithPaymentFromConfig } from '@x402/fetch';
import { privateKeyToAccount } from 'viem/accounts';
import { createWalletClient, createPublicClient, http, getAddress, parseGwei } from 'viem';

const megaethChain = {
  id: 4326, name: 'MegaETH',
  nativeCurrency: { name: 'Ether', symbol: 'ETH', decimals: 18 },
  rpcUrls: { default: { http: ['https://mainnet.megaeth.com/rpc'] } },
};

const erc20TransferAbi = [{
  type: 'function', name: 'transfer', stateMutability: 'nonpayable',
  inputs: [{ name: 'to', type: 'address' }, { name: 'value', type: 'uint256' }],
  outputs: [{ name: '', type: 'bool' }],
}];

// Custom scheme: sends USDm transfer, returns txHash
class MegaethScheme {
  constructor(wc, pc) {
    this.scheme = 'exact'; this.wc = wc; this.pc = pc;
    this.nonce = null; this.queue = Promise.resolve();
  }
  createPaymentPayload(x402Version, req) {
    const run = async () => {
      const to = getAddress(req.payTo);
      const token = getAddress(req.asset);
      const value = BigInt(req.amount);
      if (this.nonce === null)
        this.nonce = await this.pc.getTransactionCount({ address: this.wc.account.address });
      try {
        const txHash = await this.wc.writeContract({
          address: token, abi: erc20TransferAbi, functionName: 'transfer',
          args: [to, value], nonce: this.nonce,
          maxFeePerGas: parseGwei('0.001'), maxPriorityFeePerGas: 0n,
          gas: 200_000n, chain: megaethChain, account: this.wc.account,
        });
        await this.pc.waitForTransactionReceipt({ hash: txHash, timeout: 5000 });
        this.nonce++;
        return { x402Version, payload: { txHash } };
      } catch (e) { this.nonce = null; throw e; }
    };
    const p = this.queue.then(run);
    this.queue = p.catch(() => {});
    return p;
  }
}

const account = privateKeyToAccount(PRIVATE_KEY);
const transport = http('https://mainnet.megaeth.com/rpc');
const scheme = new MegaethScheme(
  createWalletClient({ account, chain: megaethChain, transport }),
  createPublicClient({ chain: megaethChain, transport }),
);
const paidFetch = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: 'eip155:4326', client: scheme }],
});

const res = await paidFetch('https://x402-gateway-production.up.railway.app/api/crypto/price?ids=bitcoin');
```
Key: USDm is 18 decimals (not 6). $0.001 = 1000000000000000 (10^15). Wallet needs USDm + tiny ETH for gas.

## Links
- GitHub: https://github.com/agentc22/x402engine-mcp
- npm: https://www.npmjs.com/package/x402engine-mcp
- Protocol: https://x402.org