The API · x402 on Base

One base URL. No account. Pay per call.

This is the machine-native API behind the catalogue. An agent calls an endpoint, receives HTTP 402 with a payment envelope, settles USDC on Base, and retries the same request. No account, no API key, no signup, no checkout page.

Read the OpenAPI spec Browse the catalogue

101 endpoints · 40 pay-per-call · 61 free · measured 06 Oct 2026

Base URL

x402.synthexforge.com

Pay-per-call routes

40

Free routes

61

Settlement

eip155:8453 · USDC

Key figures

Counted from the live service

Every number on this page is measured from the running API — its route table, its OpenAPI spec, and an unpaid probe of each route. Nothing here is illustrative or projected.

Pay-per-call routespaid per call in USDC on Base

Free routes17 verify · 22 public keys

Endpointsone base URL, one signing key

Service familiesgrouped by the job they do

101 paths / 53 GET / 48 POST · measured 06 Oct 2026 · re-verified before deploy

How a paid call works

Four steps, and the agent does all of them

This is the part most integrators have not seen before. There is no dashboard in the loop and nothing to sign up for — the payment challenge rides the request itself.

01
Call it, unpaid
The agent sends an ordinary HTTP request to a pay-per-call endpoint — with no payment attached and nothing to authorise first.
POST /v1/invoice-ocr
02
Receive 402
The service answers HTTP 402 with a PAYMENT-REQUIRED envelope naming the scheme, network, asset, amount and payTo address. This is the quote.
402 · PAYMENT-REQUIRED
03
Settle in USDC
The agent signs an EIP-3009 transferWithAuthorization for the stated amount on Base. No account, no API key, no signup — the signature is the authorisation.
eip155:8453 · 0.35 USDC
04
Retry and receive
The identical request is sent again with the payment attached. The service performs the work and returns a signed, re-verifiable result.
application/json · Ed25519 signed

Try it without paying

Send a request to any pay-per-call endpoint with no payment header. You get the 402 and the envelope back — a complete, real quote for the call, and no charge.

curl -i -X POST https://x402.synthexforge.com/v1/invoice-ocr

The catalogue

All 40 pay-per-call endpoints

Grouped by the job they do. Every price below is read from the service's own route table and re-confirmed by an unpaid probe — not copied from prose. The free verification routes sit alongside each family, so a buyer can check our claims before paying.

Governance

The agentic-commerce control plane: the Bureau verifies any x402 endpoint, the Governor authorises spend before it happens.

5 pay-per-call · 13 free

POST /v1/bureau/audit
$0.25
x402 Bureau — full conformance audit of any endpoint (PAID $0.25)
POST /v1/bureau/receipt-check
$0.05
x402 Bureau — conformance-check any issuer's receipt/offer (PAID $0.05)
POST /v1/bureau/reputation
$0.10
x402 Bureau — reputation from signed observation history (PAID $0.10)
POST /v1/governance/reserve
$0.02
Agent Spend Governor — ATOMIC reserved lease (PAID $0.02)
POST /v1/governance/settle
$0.02
Agent Spend Governor — settle a lease, idempotent (PAID $0.02)

Free verify/v1/bureau/anchor/verify · /v1/bureau/verify · /v1/governance/verify

Trust & Reputation

Prove who an agent is, what it has done, and that the record has not been altered.

7 pay-per-call · 14 free

POST /v1/agent-reputation
$0.25
Agent Reputation
POST /v1/agent-reputation/trusted-route
$0.30
Agent Reputation Trusted Route
POST /v1/identity/control-proof
$0.20
Identity Control Proof
POST /v1/readiness/attest
$0.25
Readiness Attest
POST /v1/receipts/mint
$0.25
Receipts Mint
POST /v1/verify-catalog/register
$0.25
Verify Catalog Register
POST /v1/veritrack/attest
$0.25
Veritrack Attest

Free verify/v1/agent-reputation/trusted-route/verify · /v1/agent-reputation/verify · /v1/identity/control-proof/verify · /v1/readiness/attest/verify · /v1/receipts/verify · /v1/veritrack/verify

Forensics & Evidence

Ingest, query, and cryptographically sign evidence so a claim can be replayed later.

4 pay-per-call · 6 free

POST /v1/data/c2pa/verify
$0.25
C2Pa Verify
POST /v1/data/signed-snapshot
$0.30
Signed Snapshot
POST /v1/evidence/ingest
$0.20
Forensics Ingest
POST /v1/evidence/query
$0.15
Forensics Query

Free verify/v1/data/verify · /v1/evidence/verify

Security & Compliance

Threat-model, scan, and check posture — the checks an autonomous actor runs on itself.

6 pay-per-call · 9 free

POST /v1/budget/preflight
$0.25
Budget Preflight
POST /v1/compliance/check
$1.00
Compliance Check
POST /v1/containment/register
$0.25
Containment Register
POST /v1/security/dependency-risk
$0.20
Dependency Risk
POST /v1/security/redteam/authorized-scan
$0.25
Redteam Authorized Scan
POST /v1/security/threatmodel
$0.25
Threatmodel Analyze

Free verify/v1/compliance/verify · /v1/containment/verify

Agent Infrastructure

The primitives an agent needs to operate: memory, tool judgement, and uptime checks.

5 pay-per-call · 8 free

POST /v1/mcp/eval/judge
$0.15
Judge Grade
POST /v1/mcp/threatmodel/tool-permission
$0.25
Tool Permission Threatmodel
POST /v1/mcp/verify/uptime
$0.25
Uptime Canary Probe
POST /v1/memory/get
$0.05
Memory Get
POST /v1/memory/put
$0.10
Memory Put

Free verify/v1/mcp/eval/judge/verify · /v1/memory/verify

Documents & Data

Deterministic extraction and transformation over documents, with redaction built in.

8 pay-per-call · 2 free

POST /v1/invoice-ocr
$0.02
Invoice Ocr
POST /v1/sec-extract
$0.05
Sec Extract
POST /v1/utils/code-review-brief
$0.15
Utils Code Review Brief
POST /v1/utils/doc-convert
$0.10
Utils Doc Convert
POST /v1/utils/invoice-extract
$0.10
Utils Invoice Extract
POST /v1/utils/pii-redact
$0.25
Utils Pii Redact
POST /v1/utils/schema-cleanup
$0.05
Utils Schema Cleanup
POST /v1/utils/translate-doc
$0.10
Utils Translate Doc

Free verify/v1/utils/verify

Research & Synthesis

Attested briefs and verdicts — synthesis an agent can cite and a third party can verify.

4 pay-per-call · 2 free

POST /v1/finance/attested-evidence
$0.35
Attested Finance
POST /v1/research/attested-brief
$2.00
Attested Brief
GET /v1/signed-research
$0.50
Signed Research
POST /v1/synthesis/verdict
$0.50
Synthesis Verdict

Free verify/v1/synthesis/verify

The 61 free routes

Verifiability is the point, not a footnote: 17 verification routes and 22 published public keys mean a third party can check a signed result without paying, without an account, and without asking us.

Verify a signed result

17 routes · Supply the signature, hash and body — free, forever, no account.

Byte-exact re-checks

7 routes · A deterministic re-run of a paid result, free by design — the output is reproducible.

Service and discovery

15 routes · Health, config, and the machine-discovery manifests.

Discovery

How an agent finds us

There is no directory to be listed in. The service publishes its own machine-readable contract, and an agent reads it before it spends anything.

Base URL

https://x402.synthexforge.com

OpenAPI spec

https://x402.synthexforge.com/openapi.json

Machine-discovery artefacts

/.well-known/x402.json
x402 v2 manifest — every pay-per-call endpoint with its price, plus the settlement terms.
200
/agent-card.json
Agent capability card — what the service can do, what each call costs, how to pay.
200
/llms.txt
Machine-readable summary for language models: the flow, the prices, the free routes.
200
/openapi.json
OpenAPI 3.1 spec — every path, method and schema, pay-per-call and free.
200

All four were fetched and confirmed to answer 200 before this page was deployed.

Signing

Ed25519

Signs x402 attestation receipts. Separate from the receive wallet’s EVM key. Every family publishes its public key on a free route.

MCP

/mcp.json

Model-driven agents can also reach part of the catalogue over the Model Context Protocol. The manifest advertises the tools, their type, and the payment rail.

Live proof

It has already settled on-chain

A paid call was made, the agent paid, and the USDC arrived in the receive wallet as an ordinary Base-mainnet transaction. Here it is — independently checkable, not a screenshot.

Transaction0x7187a99ab00c5cfa0744700ecbf14d4038bb9d68e3b385a9ccab583841b6f9ef

0.35 USDC to the receive wallet, confirmed 0x1 (success). Verify it yourself on Basescan — the link goes to the transaction, not to a picture of it.

Open on Basescan ↗

Network

Base mainnet (eip155:8453)

Asset

USDC

Amount

0.35 USDC

Block

51,451,099

Independent verification

PayAPI Market paid for a real call from its own wallet and received product back.

That is a third party paying us end to end without our involvement — the settlement path working exactly as a buyer would experience it.

Start here

Read the contract, then make a call.

The spec is public, the prices are published, and the first thing you will receive is a real quote. Nothing to sign up for.

Read the spec ↗See the catalogue

https://x402.synthexforge.com