How to Enable PayAI x402 Facilitator for USDC (2026)

AI agents that sell HTTP resources still need a facilitator that verifies a signed stablecoin payment and settles it on-chain before the response leaves the server.

The named object is the PayAI x402 Facilitator at facilitator.payai.network: a production verify/settle service for exact (and related) x402 payments across Solana, Base, Polygon, Avalanche, Arbitrum, Sei, X Layer, and SKALE. Wire it with @payai/facilitator plus HTTPFacilitatorClient and Express paymentMiddleware. That is not Nevermined plan metering with nvm:erc4337, not Circle's public facilitator alone, not Coinbase AgentKit as a buyer client, not Cloudflare Agents MCP paywalls, and not Alchemy gateway auth.

Facts below come from PayAI's x402 quickstart, facilitator introduction, Express server quickstart, facilitator pricing, and accept payments from AI agents docs, plus live GET /supported and GET /pricing on facilitator.payai.network as of October 1, 2026. Rates, free-credit counts, network lists, package names, and endpoint paths are taken from those sources. No invented fee schedules.

Key Takeaways

• Point Express paymentMiddleware at PayAI via @payai/facilitator and HTTPFacilitatorClient (no manual facilitator URL).
• Start on free allowance: 1,000 lifetime free credits per receiving wallet; testnets do not consume it.
• Register ExactEvmScheme / ExactSvmScheme for the networks in your accepts array (e.g. Base Sepolia + Solana Devnet).
• Beyond free, cost-plus is network gas × 1.30 in credits (1 credit = $0.001); set PAYAI_API_KEY_ID/SECRET.
• Named downside: shared host/IP pools can burn the free allowance early; get a key before production bursts.

Who this is for

Use this path if you expose an API, SaaS operation, or agent-facing HTTP resource, you want buyers (including AI agents) to pay in USDC or Solana USDC under the x402 exact scheme, and you can run TypeScript Express (or Hono/FastAPI/Flask/Gin with the matching PayAI guides).

Skip it if you need Nevermined plan objects and capped createDelegation (see How to Enable Nevermined x402 USDC Payments for AI Agents), only Circle's facilitator without PayAI packages (see How to Enable Circle x402 Facilitator for USDC), buyer-side AgentKit payments (see How to Pay for an x402 API with Coinbase AgentKit), MCP tool paywalls on Cloudflare (see How to Charge for MCP Tools with Cloudflare Agents x402), or Alchemy RPC auth (see How to Authenticate Alchemy APIs with x402 USDC). For picking among facilitators, see How to Choose an x402 Facilitator for USDC. For generic accept-side patterns, see How to Accept x402 USDC Payments from AI Agents.

What the PayAI x402 Facilitator does

x402 revives HTTP 402 Payment Required. The resource server advertises payment requirements; the client signs a stablecoin payment; the facilitator verifies the payload and settles on-chain so the server never holds a merchant private key or runs its own RPC wallet loop.

PayAI's production origin is https://facilitator.payai.network. Documented endpoints include GET /supported, POST /verify, POST /settle, and GET /discovery/resources (the Bazaar). Ordinary exact payments can start without portal signup or an API key within the free allowance. PayAI does not custody merchant balances and is not a card/fiat checkout processor.

Stablecoin Insider's working definition: enable the facilitator when middleware can call verify before work and settle after success, with network coverage and rate limits you can operate against. Discovery via Bazaar is optional; it helps agents find priced routes but does not replace your own docs.

Prerequisites

You need a receiving wallet address on each network you price (an EVM hex address and/or a Solana base58 address), Node.js with TypeScript (or another documented stack), and a disposable funded buyer wallet to prove settle, not just a 402 response. On Solana, PayAI notes the merchant USDC ATA must exist; creating it needs a setup fee payer with SOL, separate from settlement gas PayAI sponsors.

You do not need a PayAI portal account for the ordinary exact starter flow. Do not add signup friction just because the SDK can take PAYAI_API_KEY_ID / PAYAI_API_KEY_SECRET. If buyers need USDC first, see How to Fund an AI Agent Wallet with USDC.

Step 1: Install packages and env

PayAI's Express quickstart installs express, dotenv, @payai/facilitator, @x402/core, @x402/evm, @x402/express, @x402/extensions, and @x402/svm. Create a project, set type: module, and add those deps as in the Express server quickstart.

Set receiving addresses in .env:

EVM_ADDRESS=0x...   # EVM wallet to receive payments
SVM_ADDRESS=...    # Solana wallet to receive payments
# Optional beyond free allowance:
# PAYAI_API_KEY_ID=...
# PAYAI_API_KEY_SECRET=...

The @payai/facilitator package points at https://facilitator.payai.network automatically. No manual facilitator URL is required for the default config.

Step 2: Wire HTTPFacilitatorClient and paymentMiddleware

Construct the facilitator client once, then pass an x402ResourceServer into paymentMiddleware with route accepts. The Express docs show dual accepts on Base Sepolia and Solana Devnet at $0.001 each:

import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { ExactEvmScheme } from "@x402/evm/exact/server";
import { ExactSvmScheme } from "@x402/svm/exact/server";
import { HTTPFacilitatorClient } from "@x402/core/server";
import { declareDiscoveryExtension } from "@x402/extensions/bazaar";
import { facilitator } from "@payai/facilitator";

const facilitatorClient = new HTTPFacilitatorClient(facilitator);

app.use(paymentMiddleware({
  "GET /weather": {
    accepts: [
      { scheme: "exact", price: "$0.001", network: "eip155:84532", payTo: evmAddress },
      { scheme: "exact", price: "$0.001", network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", payTo: svmAddress },
    ],
    description: "Weather data",
    mimeType: "application/json",
    serviceName: "Weather API",
    tags: ["weather", "api"],
    extensions: { ...declareDiscoveryExtension({ output: { example: { report: { weather: "sunny", temperature: 70 } } } }) },
  },
}, new x402ResourceServer(facilitatorClient)
  .register("eip155:84532", new ExactEvmScheme())
  .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme()));

Keep health checks and public docs free. Only meter the bounded operation (report, inference, premium lookup). Payment proves payment, not permission to another customer's private data; keep normal auth on user-scoped routes.

Step 3: Prove unpaid 402, then a real settle

Run the server (npx tsx index.ts in the Express guide; default listen example is port 4021). Hit the route without payment and confirm HTTP 402 with the expected recipient, asset, network, and price. Then run a funded buyer from PayAI's fetch or Axios client quickstarts and retain evidence of a successful paid response plus finalized on-chain settlement.

PayAI's accept-payments guide is explicit: a 402 alone does not prove the integration. Reconcile ambiguous responses before retrying; settlement_pending on POST /settle means unresolved, and identical-body retries are idempotent. Optionally publish Bazaar discovery metadata so agents can find the route.

Step 4: Move to mainnet and scale past free credits

For mainnet, update each route's network and the matching .register(...) scheme together (for example Base eip155:8453 and Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp). Adding credentials alone does not switch networks. PayAI documents that ordinary exact mainnet payments can run within the free allowance without an API key.

Beyond the allowance, authenticate. Autonomous agents can buy credits and a key over x402 without portal signup; humans can use merchant.payai.network. Set PAYAI_API_KEY_ID and PAYAI_API_KEY_SECRET; @payai/facilitator picks them up automatically. Exhausting free tier returns HTTP 403 with errorReason beginning free_tier_exhausted.

Pricing and free allowance (sourced)

Per PayAI's facilitator pricing page (cost-plus live since 21 September 2026): new receiving wallets get 1,000 lifetime free credits (not a monthly reset). Testnet settlements are free and do not consume the allowance. Beyond free, each settlement costs measured network gas × 1.30, billed in credits at 1 credit = $0.001. Live rates are at facilitator.payai.network/pricing and under pricing on GET /supported.

Stablecoin Insider checked live GET /pricing on October 1, 2026: Base exact EIP-3009 was 2.31 credits ($0.00231) per settlement; Solana mainnet exact was 1.62 credits ($0.00162); Base Sepolia and Solana Devnet exact were 0. Treat the live pricing table as authoritative because rates refresh with gas and token prices.

Supported networks snapshot

PayAI's quickstart lists Arbitrum One/Sepolia, Avalanche/Fuji, Base/Base Sepolia, Polygon/Amoy, Sei/Sei Testnet, SKALE Base/Sepolia, Solana/Devnet, and X Layer/Testnet, with v1 short names and v2 CAIP-2 IDs. Always confirm against live GET /supported before you hard-code a network string. A payment kind leaving /supported is the withdrawal signal.

How PayAI compares to Circle CDP and Nevermined

PayAI wins when you want a ready multi-network facilitator with a typed npm entrypoint and optional agent-buyable credits. Nevermined wins when plan IDs and createDelegation are the product. Circle wins when your stack already centers Circle's facilitator. For a broader shortlist, use How to Choose an x402 Facilitator for USDC.

Stablecoin Insider's take

FAQ

How to Choose an x402 Facilitator for USDC (2026)

Compare x402 facilitator options for USDC agent and API payments.

Stablecoin Insider

This content is provided for informational and educational purposes only and does not constitute financial, investment, legal, or tax advice; no material herein should be interpreted as a recommendation, endorsement, or solicitation to buy or sell.