Z-ZERO MCP — Payment Infrastructure for Agentic Commerce (USDC on Base, gasless)

AI Agents today can plan, reason, and code — but they are financially blind. They cannot hold money, make payments, or prove their trustworthiness. Every purchase still requires a human to copy-paste a credit card number.

Z-ZERO fixes that. One MCP server gives your agent (Claude, Cursor, any MCP-compatible client) two payment rails — gasless USDC on Base for crypto-native checkouts, and JIT single-use virtual cards for the 99% of the web that only takes cards — while the model never sees a real card number.

npx z-zero-mcp-server

What makes it different:

• 🔐 Zero-trust by design — the AI never sees PAN, CVV, or expiry. Card data exists only in RAM, injected via Playwright at the last step, then wiped.

• ⛽ Gasless USDC on Base — auto-detects crypto checkout (EIP-681) and settles as a gasless USDC transfer sponsored by Coinbase Paymaster. The agent holds only USDC — no ETH, no gas UX.

• 💳 JIT single-use virtual cards — amount-locked, 1-hour TTL, burned after a single use. Fiat fallback for the rest of the web.

• 🧠 Smart Routing + checkout intelligence — get_merchant_hints serves platform-specific checkout playbooks (Shopify, Etsy, WooCommerce…).

• ✍️ Signed intent + signed receipt — the card is bound to a signed statement of what it is for, and every confirmed purchase returns a signed receipt with a diff against that intent. The agent can prove a purchase instead of claiming one (verify_receipt, public verify page).

• 🔄 Structured failure labels — failed checkouts are labeled with a fixed 14-class failure_class (automatically, not only when an agent remembers to report) and stored as evidence for the merchant knowledge base. Facts are promoted into shared hints only after a later outcome or review verifies them.

Live on Base Mainnet

• ✅ Proof — real gasless USDC transfer on Base mainnet: 0xdfd1f2f8…5d7a

• Onboarding is just "deposit USDC" — no seed phrases in the agent, no native gas token, no exchange account.

Related MCP server: AgentPay

How It Works

 User            AI Agent              MCP Tools              Z-ZERO API
  │                  │                      │                      │
  │ "Buy me this     │                      │                      │
  │  Shopify item"   │                      │                      │
  ├─────────────────▶│                      │                      │
  │                  │ read mcp://resources/sop (MANDATORY)        │
  │                  ├─────────────────────▶│                      │
  │                  │◀── platform rules ───┤                      │
  │                  │    + payment SOP     │                      │
  │                  │                      │                      │
  │                  │ get_merchant_hints("_platform_shopify")     │
  │                  ├─────────────────────▶│  GET /checkout-hints │
  │                  │                      ├─────────────────────▶│
  │                  │◀── pre_steps+notes ──┤◀──── hints data ─────┤
  │                  │                      │                      │
  │                  │ (fills shipping form, reaches payment page) │
  │                  │                      │                      │
  │                  │ request_payment_token(amount, card_alias)   │
  │                  ├─────────────────────▶│                      │
  │                  │◀── temp_auth token ──┤   (1-hour TTL)       │
  │                  │                      │                      │
  │                  │ execute_payment(token, checkout_url)        │
  │                  ├─────────────────────▶│                      │
  │                  │      Playwright auto-fills card form,       │
  │                  │      burns token after single use 🔥        │
  │                  │◀──── ✅ success ─────┤                      │
  │ "Done! Your item │                      │                      │
  │  is ordered."    │                      │                      │
  │◀─────────────────┤                      │                      │

The AI agent never touches card data — it only handles single-use tokens. Real card details are injected by Playwright at the last step and wiped from RAM.

Crypto checkout branch: when auto_pay_checkout detects a crypto-native checkout (EIP-681), it skips the card flow entirely and settles as a gasless USDC transfer on Base — see above.

Why Z-ZERO

Z-ZERO is not a checkout bot — it's payment infrastructure for the agentic-commerce era (agentic transactions are projected to reach $1.5T by 2030 — Juniper Research).

Today, the web is built for humans: agents must fill forms and click buttons, and every purchase still needs a human's card. Z-ZERO solves that now — JIT single-use virtual cards + gasless USDC on Base, with card data isolated from the model. Tomorrow, agent payments become a standardized protocol — and what we build along the way is the long-term value:

• Shared checkout intelligence — every transaction (and every failure) makes the network smarter.

• An open standard for agent payments — any agent platform plugs in via MCP; any rail (cards, USDC, x402) can be added.

• KYA — Know Your Agent — verifiable agent reputation. The question isn't "can this agent pay?" but "should you trust it to?"

📖 Full vision & architecture: The Z-Zero Whitebook

Quick Install (Recommended)

npx z-zero-mcp-server

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "z-zero": {
      "command": "npx",
      "args": ["-y", "z-zero-mcp-server@latest"],
      "env": {
        "Z_ZERO_API_KEY": "zk_live_your_passport_key_here"
      }
    }
  }
}

Get your Passport Key at: z-zero.xyz/dashboard/agents

Security: rotate-on-connect (v1.5.0+)

The key you copy from the dashboard (or paste into a chat) is only a one-time bootstrap ticket. The moment your agent connects with it, the MCP server silently swaps it for a fresh key:

• The fresh key travels server → MCP process → disk and is stored in ~/.z-zero/credentials (mode 0600). It never appears in any LLM conversation, tool result, or config file.

• The pasted key is dead within seconds — a copy living in a chat transcript, clipboard, or screenshot can no longer be used by anyone.

• On startup the MCP loads the key from ~/.z-zero/credentials first; the Z_ZERO_API_KEY env var is only a bootstrap fallback.

One key = one machine. All agents on the same machine (Claude Desktop, Claude Code, Cursor, …) share the same MCP install and the same credentials file — install once, every agent can pay. Connecting a different machine with a copied key rotates it, which instantly disconnects the original machine. That is deliberate: it blocks key sharing and doubles as an intrusion alarm — if your agent suddenly fails auth, someone else used your key; go to the dashboard and revoke.

Older self-hosted backends without the rotate endpoint keep working — the pasted key simply stays active as before.

Requirements

• Node.js v18+ — nodejs.org

• Passport Key — starts with zk_live_, get it from the dashboard above

Available MCP Tools

Group 1 — Wallet Config (Passive)

Group 2 — Manual 4-Step Payment (Active)

Group 3 — Smart Autopilot

📖 Note: Version checking is handled automatically in each API call. No separate tool needed.

Agent primitives (v1.7.0)

Three things an agent can do here that it cannot do with a normal virtual card.

1. Signed intent — the card knows what it is for

Pass the cart when you request a token:

request_payment_token({
  card_alias: "Card_01",
  amount: 44.00,
  merchant: "etsy.com",
  cart: [{ title: "Ceramic mug — matte white", qty: 2, unit_price: 18.50 }],
  ship_to: "12 Nguyen Hue, District 1, Ho Chi Minh City, VN"
})

Z-ZERO signs that statement (EIP-191) and binds it to the card. The user gets cryptographic proof of what this card was authorized to buy — not just how much it could spend. The shipping address is stored as a hash, never raw.

Before you request a token, compare the checkout page with what the user actually asked for — same items, same quantity, same variant, same destination. A mismatch you catch there costs nothing. After the token, it costs a card.

2. Signed receipt — prove the purchase, don't claim it

On a confirmed payment you get back:

"signed_receipt": {
  "receipt_id": "8ea36791-…",
  "receipt_hash": "0x…",
  "match": { "total": "over", "domain": "ok" },
  "diff":  [{ "field": "total", "expected": 44.00, "observed": 46.75 }],
  "verify_url": "https://z-zero.xyz/receipt/8ea36791-…"
}

diff is the part that matters: it is what the merchant actually did versus what was authorized. Share verify_url with the user — the page is public and anyone can check it. Verification is three checks: the signature is valid, the signer is Z-ZERO, and the fields shown still hash to what was signed (so editing the record afterwards is detectable, including by us).

What a valid receipt does and does not prove. It proves the record is signed by Z-ZERO and unaltered. It does not by itself prove the merchant charged what the receipt says — most fields start life as the agent's reading of a web page. Every receipt therefore carries provenance per field: zzero_issued (the limit we set), issuer_captured (confirmed by the card issuer's capture webhook — settlement evidence), agent_reported (unverified), human_verified. Until the capture webhook lands, this is a signed execution receipt, not settlement proof, and it says so.

3. Structured failure classes — every failure teaches the network

report_checkout_fail takes a fixed enum, not free text:

card_declined_issuer · card_declined_bin_block · avs_mismatch · 3ds_required · bot_detected · form_changed · price_changed · out_of_stock · shipping_unsupported · login_required · timeout · outcome_unconfirmed · intent_mismatch · unknown

Failed runs are also labeled automatically from the browser outcome, so the network learns even when nobody remembers to report. Card numbers are redacted at capture — they never reach a log, screenshot or DOM dump.

REST API Reference

The Z-ZERO backend is hosted at https://z-zero.xyz. All endpoints require a Bearer token using your Passport Key.

⚠️ Use the MCP tools above instead of calling REST directly. If you must call REST, use the exact paths below.

GET /api/tokens/cards

Returns your card list, balance, and deposit addresses.

curl -X GET "https://z-zero.xyz/api/tokens/cards" \
  -H "Authorization: Bearer zk_live_your_key"

Aliases (also work):

• GET /api/v1/cards ← for agents that guess REST-style paths

POST /api/tokens/issue

Issue a JIT payment token.

POST /api/tokens/resolve

Resolve a token to card data (server-side only).

POST /api/tokens/burn

Burn a used token.

POST /api/tokens/cancel

Cancel an unused token (refunds balance).

Troubleshooting

"Z_ZERO_API_KEY is missing"

1. Go to z-zero.xyz/dashboard/agents

2. Copy your Passport Key (starts with zk_live_)

3. Add it to your config as Z_ZERO_API_KEY

4. Restart Claude Desktop / Cursor

"Invalid API Key" (401)

• Double-check you copied the full key (e.g. zk_live_c0g3l)

• Make sure there are no extra spaces or line breaks

"404 Not Found" on /api/v1/cards

• This is a legacy path alias — it should now work. If not, use /api/tokens/cards directly.

Security: the key you paste is never kept — it rotates the moment your agent first connects, and the fresh key lives only in a local owner-only file (~/.z-zero/credentials, mode 0600), never in any LLM conversation. Card data exists only in volatile RAM during execution.