Spend Gate: KI-Agenten pruefen Zahlungen vor der Ausgabe fuer 0,005 USDC

Posted on Oct 27 • Originally published at scriptmasterlabs.com

It buys a check first. ScriptMasterLabs' Spend Gate — live-tested October 26, 2026 — charges $0.005 USDC on Base for a pre-payment verdict: four independent paths vote pay or reject on the payee and the quoted amount, the votes combine into a coherence score (|Σ w·d| / Σ w, pass at ≥ 0.6 with a pay-side consensus), and a Jev decision model reviews the payment only if the gate passes. In the October 26 proof runs the gate passed a $0.001 USDC call at coherence 1.0 and blocked a $5.00 over-cap call at coherence 1.0 — consensus reject, Jev never fired, zero decision-model spend on the block.

That is the short answer, with the receipts below. Spend Gate is the decision-gated payments pattern ( https://scriptmasterlabs.com/decision-gated-payments ) pointed at the buyer's side of x402: the rails move money, the gate decides whether this payment should move. The taxonomy argument for the missing decision layer is at https://scriptmasterlabs.com/the-fourth-layer — this page is the operational version, with a live endpoint, a price, and settled proof transactions for both a pass and a block.

An agent (or its wallet wrapper) sends the gate a payee and a quoted amount before signing anything. Four paths evaluate the payment independently — path independence is the point: a number computed from paths that copy each other would claim agreement that never happened.

Default caps (in code and in the product docs): data_lookup / search / content_fetch / verification $0.05, market_data $0.10, inference / llm $0.25, compute $0.50, unlisted category $0.10.

The votes combine as coherence = |Σ w·d| / Σ w, where d = +1 for pay-side, −1 for reject-side, and w is each path's confidence. gate_pass requires coherence ≥ 0.6 AND a pay-side consensus. Only on a pass does the second opinion fire: Jev (jev-1.14.0 in the proof runs) answers an act score plus a pay / reject / quarantine choice. A block spends nothing on Jev — the expensive judgment is reserved for payments that already cleared the cheap evidence.

The check itself is an x402 call, so the pattern eats its own cooking: MCP tool spend_gate_check and REST POST /x402/spend-gate on the mcp-x402 host, $0.005 USDC per check on Base (eip155:8453) to payTo 0xc29185fa176357612f3194735753e520e91adc46. The gate moves no funds — it returns a verdict; the agent's own wallet still signs (or doesn't) afterwards.

Every check below was paid by ScriptMasterLabs' own proof wallet and settled to the fleet's own payTo — owner self-tests, never customer purchases — and every transaction was re-read on Base RPC on the evening of October 26, 2026 for this page: all six at status 0x1 (success).

Details that matter more than the headline numbers:

ScriptMasterLabs' Spend Gate, live-tested October 26, 2026, passed a $0.001 USDC payment at coherence 1.0 and blocked a $5 over-cap payment at coherence 1.0 — the check itself costs $0.005 USDC, settled on Base.

Fresh unpaid probes for this page, run twice with identical amounts and statuses (probe file: probe-spendgate-1026.out in the run record):

Minimal REST shape (unpaid call returns the 402 challenge first; pay $0.005 and re-present):

POST https://mcp-x402.onrender.com/x402/spend-gate { "payee": "https://seller.example/api", "quote_usdc": 0.001, "tool_category": "data_lookup", "policy_cap_usdc": 0.05, "manifest_url": "https://www.npmjs.com/package/express" } Enter fullscreen mode Exit fullscreen mode The product Spend Gate is live as part of ScriptMasterLabs' mcp-x402 node: MCP tool spend_gate_check for MCP clients, REST POST /x402/spend-gate for anything that speaks HTTP, $0.005 USDC per check on Base, no account and no API key — the x402 challenge is the checkout. It is the buyer-side companion to the seller-side decision products: Verdict Protocol ( https://scriptmasterlabs.com/verdict-protocol ) seals a 5-juror Jev decision receipt for $0.25 when the question is a judgment call worth a jury; Spend Gate is the half-cent evidence check for the ordinary payment an agent makes a hundred times a day. The pattern both implement — decide first, pay second, keep the receipt — is written up at https://scriptmasterlabs.com/decision-gated-payments

Canonical: https://scriptmasterlabs.com/ai-agent-spend-gate Related: https://scriptmasterlabs.com/verdict-protocol · https://scriptmasterlabs.com/decision-gated-payments · https://scriptmasterlabs.com/the-fourth-layer · https://scriptmasterlabs.com/x402-agent-spending-guard