The x402 protocol has gone from "cool idea" to "actually shipping" faster than most crypto infrastructure. Coinbase and Cloudflare launched it in May 2025. Six months later: 100M+ payments processed, V2 shipped with multi-chain support, and three hyperscalers (AWS, Google Cloud, Circle) announced their own implementations within 30 days of each other.
But the part that matters to builders is this: you can now charge per API call in USDC without a merchant account.
Here are 5 live MCP servers that prove it.
1. Kiro Crypto Signals — TA + Decision Audit
What it does: Real-time technical analysis (RSI, MACD, EMA, Bollinger, ATR) with a BUY/SELL/HOLD decision and a unique decision_id for audit trails.
Free preview: GET /signal/BTC/preview — no wallet needed.
Paid endpoints:
-
/signal/:symbol— $0.01 USDC (full signal + decision) -
/indicators/:symbol— $0.005 USDC (raw indicators only) -
/screener— $0.02 USDC (top 28 symbols, ranked)
Why it matters: It's one of the few x402 services that gives you an audit trail. Every decision gets a decision_id. You can come back later and verify whether the signal was actually correct against real market data.
Base mainnet. No API key. Just a wallet with a few cents of USDC.
2. Cryptorefills — Agent Commerce
What it does: Gift cards, mobile top-ups, and eSIMs via x402 checkout.
Launched May 12, 2026 — one of the most concrete "agent commerce" implementations to date. An AI agent can literally buy a gift card programmatically.
They also publish an open-source operations reference for the merchant layer — 9 playbooks, TypeScript schemas, 5 runnable examples. Clone it and watch the agent-merchant exchange execute against production.
3. Onyx Actions — Unstick Your Agent
What it does: Captcha OCR + SMS OTP via real carrier SIM.
Every agent builder hits the same wall: signup forms. Onyx solves it with MCP-native tools at /mcp/, REST fallback, and a full Bazaar-discoverable manifest at /.well-known/x402.json.
Pricing:
- Captcha OCR: $0.003 USDC (~30ms, 70-90% accuracy)
- SMS OTP: $0.05 USDC (delivered via real carrier SIM with demo mode)
4. TensorFeed — AI Industry Intelligence
What it does: Real-time AI news, model pricing, uptime monitoring, provider deep-dives.
15 paid tools including cost projection, model routing recommendations, and webhook watches with daily/weekly digests.
Pricing: $0.02 USDC per credit on Base, with volume discounts at $5 / $30 / $200 tiers.
Already in the official MCP registry as ai.tensorfeed/mcp-server with DNS verification.
5. ZKProofport — Identity Without Exposure
What it does: Zero-knowledge proofs for Coinbase KYC, country, Google OIDC, Workspace, and MS 365 — without revealing personal data.
AWS Nitro Enclave TEE proving. ERC-8004 registered (token ID 25331). x402 USDC on Base.
Won 1st place at The Synthesis Hackathon ("Agents That Keep Secrets" track, April 2026).
The Pattern
Every one of these services shares the same architecture:
- HTTP endpoint with x402 middleware
-
402 response with
payment-requiredheaders - USDC settlement on Base (200ms finality)
- No API keys, no accounts, no subscriptions
For MCP servers specifically, the protocol is: agent calls a tool → server responds 402 with price → agent pays → tool executes. That's it.
Try It
If you have a wallet with $0.50 of USDC on Base, you can call all of the above services in the next 10 minutes. No registration. No KYC. No monthly fee.
The x402 ecosystem is still early — 891 services on Agentic.Market, ~$600M annualized run rate across all implementations — but the part that works today is real money moving between real APIs.
If you're building an MCP server, the question isn't whether to add payments. It's whether you can afford not to.
Disclosure: I built #1 (Kiro Crypto Signals). The other 4 are independent services I found while mapping the ecosystem. All endpoints were verified live as of May 2026.
