Don't trust the answer. Verify it.
59 verified calculators — tax, crypto, lending, retirement, business — priced per call in USDC, no account or API key. The difference: every answer ships its 2026 source, a formula trace, and a reproducible hash — and an agent can re-derive it for free at /v1/golden/:id. You don't trust the server; you verify the math.
See it work, right now.
These run the real engines behind the paid API — the exact 2026 math an agent pays for, shown as a free rounded preview. Pick a tool and change anything.
Social Security portion caps at the 2026 $184,500 wage base.
59 verified endpoints, and growing.
New tools ship regularly across tax, crypto/DeFi, lending, real estate, retirement, and business. Every answer is checked against hand-verified reference values before it ships, and carries its formula, data vintage, and a reproducible hash. Single calls from $0.02; multi-jurisdiction reports run $0.25–$1.00.
Every answer, as a receipt you can defend.
A number you have to stand behind — to the IRS, FINRA, or an AI-liability insurer — needs a record, not just a result. Pay the professional tier and the answer comes back as a portable, signed Verification Receipt an auditor can re-derive without trusting us. POST /v1/receipt/:id — $1 a call, $5 a report.
Same hash, re-derivable
Carries the SHA-256 over {endpoint, inputs, result, method, dataVintage} — anyone re-derives it free at /v1/golden/:id.
Ed25519 issuer attestation
Attests who issued the receipt and when. Correctness is still proven by re-derivation — the signature never blesses the number.
On-chain identity
Ties the issuer to ERC-8004 agent 59110 on Base — a public, checkable identity for the record.
Pay one call in five lines.
A funded Base wallet key is the only setup. @x402/fetch wraps fetch, so your agent runs the whole 402 → sign → retry round trip on a single call — no accounts, no API keys, no invoices. The reply carries the verified result and a reproducible provenance hash.
// npm i @x402/fetch @x402/evm viem · one funded Base wallet key import { wrapFetchWithPaymentFromConfig } from "@x402/fetch"; import { ExactEvmScheme } from "@x402/evm"; import { privateKeyToAccount } from "viem/accounts"; const pay = wrapFetchWithPaymentFromConfig(fetch, { schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(privateKeyToAccount(process.env.BASE_WALLET_KEY)) }] }); const res = await pay("https://x402toll.com/v1/paycheck", { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ salary: 85000, state: "TX" }) }); const { result, provenance } = await res.json(); // verified result + reproducible hash
Evaluate for free first — no wallet. Before paying, an agent can hit GET /v1/catalog (prices + schemas), POST /v1/preview/:id (a rounded result), or GET /v1/golden/:id (the expected result + hash to check against). Or point Claude / Cursor at the free discovery MCP — npx tollbooth-x402 — and call tollbooth_quote (the exact price and response shape for any tool), tollbooth_catalog, tollbooth_preview, or tollbooth_golden to see everything before spending a cent.
Four steps. One round trip.
x402 turns HTTP's dormant 402 status into a payment rail. Your agent does all four automatically on one retry — no signup, no key, no invoice.
Request
POST the inputs to any endpoint, no auth.
Quote
Server returns the price + pay-to address in a header.
Pay
Agent signs a USDC authorization, retries. No gas.
Answer
Result + provenance; settlement lands on Base in seconds.
Verify any answer — even one you got elsewhere.
Tollbooth is also a neutral place to check answers. Each surface returns pass/fail and field names only — never the value — so you can confirm a number without buying it.
Confirm a claim
POST /v1/verify — confirm or deny a number from any source (another model, a spreadsheet, a vendor) against our engine.
Signed compliance report
POST /v1/verify/batch — batch up to 100 claims into one signed, filable report an enterprise can archive.
GVP conformance check
POST /v1/gvp/check — check any GVP answer's own hash + completeness; mints a “self-consistent · reproducible” badge (not an endorsement).
Try the hash re-check: paste a paid response and its inputs to re-derive the SHA-256 and confirm nothing was altered — free, and provable by anyone.