x402-gateway — 21 Pay-Per-Call APIs for AI Agents (USDC on B

x402 Gateway APIs

21 pay-per-call APIs for AI agents — blockchain data, web scraping, ZK proof verification, QR/diagram/OG-image rendering, LLM chat, gift cards. Settled in USDC on Base via the x402 payment protocol. No accounts, no API keys: agents pay per request via the x402 protocol.

x402 Payment Protocol

Pay-per-call MCP.
No accounts. No logins. No keys.

21 tools on Base via the Coinbase CDP x402 facilitator.

Agents pay per request in USDC — settled on-chain in seconds.

No API keys to provision, no subscriptions to manage.

21 Tools live
$0.001 Starting price
<2s Response time
USDC on Base

How it works

The x402 protocol turns HTTP 402 Payment Required into an onchain payment flow.

1

Agent reads metadata

GET the endpoint. Receive an OpenAPI spec + x402 payment details (payTo, amount, asset, network).

2

Sees 402 response

Server returns HTTP 402 with a signed payment requirement in USDC on Base or Solana.

3

Signs & pays onchain

Agent wallet broadcasts a USDC microtransaction on Base. No human needed, no account to create.

4

Gets the result

Server verifies the payment header and returns the API response. Done.

All APIs

Each tool is a standalone paid endpoint. Browse the catalog — click any card for details.

markdown $0.001

Fetch a URL and convert its main content to clean, LLM-ready Markdown. Strips nav/ads/sidebars.

POST
token_price $0.002

Get the live price of a token by symbol (e.g. ETH, USDC, MATIC).

GET
wallet_portfolio $0.002

Get a complete wallet portfolio: native ETH balance, ERC-20 balances, NFT holdings, recent transfers.

POST
whale_alerts $0.002

Scan recent blocks for large ETH transfers involving an address. Filter by direction and threshold.

POST
cross_chain_balance $0.002

Aggregate native balance and token/NFT counts for an address across eth, arb, base, polygon, opt.

POST
changelog_openapi $0.005

Diff two OpenAPI specs and generate a structured breaking-change changelog. Deterministic, no LLM.

POST
changelog_git $0.005

Diff git commits and generate a structured breaking-change changelog. Provide repo URL + base commit.

POST
mermaid $0.005

Render a Mermaid diagram to an image (PNG or SVG). Returns base64-encoded image.

POST
html_to_markdown $0.001

Convert an HTML string to clean, LLM-ready Markdown. Handles headings, links, tables, code blocks.

POST
qr_generator $0.001

Generate a QR code or barcode as an image (SVG or PNG). QR, Code128, EAN, UPC, ISBN, and more.

GET
og_image_generator $0.001

Generate an Open Graph social-card image (1200x630 PNG) from a title and description.

GET
jobs $0.002

Search live job postings by keywords and locations. Returns structured results: title, company, location, salary, and more.

POST
verify_semaphore $0.001

Verify a Semaphore ZK proof locally using Groth16 (embedded official vkey). No external dependency — pure on-device verification.

POST
verify_worldid $0.005

Verify a World ID 4.0 proof via the Worldcoin Developer Portal API. Generates RP signature, proxies to Worldcoin, returns nullifier + validity.

POST
verify_batch $0.005

Batch verify up to 10 Semaphore proofs in a single request. Returns per-proof results with timing stats.

POST
wallet_verify_siwe $0.001

Verify a Sign-In-With-Ethereum (EIP-4361) signature as a paid oracle: returns wallet address + chainId, mints nothing.

POST
wallet_verify_nostr $0.001

Verify a NIP-98 Nostr HTTP auth event with replay protection (each event id verifies once). Returns the signer pubkey.

POST
wallet_verify_solana $0.001

Verify an ed25519 Solana wallet signature over a nonce-bearing message. One verification per nonce; returns signer pubkey.

POST
wallet_checksum $0.001

Convert an Ethereum address to its EIP-55 checksummed form — required on SIWE message line 2 before signing.

POST
llm_chat $0.001

Chat with a language model. OpenAI-compatible /v1/chat/completions. 50+ models — free (auto, eco, premium) are $0, paid models at cost.

POST
giftcard_buy dynamic

Buy a digital gift card code (Foot Locker, Target, AMC, 1000+ brands). Search the catalog free, pay the face value + fee in USDC — code delivered instantly, settled on Base via x402.

POST

How payment works

Send a POST to any tool endpoint without a payment header and the API replies 402 Payment Required with an x402 challenge (payTo address, amount in USDC, asset contract, network). Your wallet signs a USDC microtransaction on Base, resubmits the request with the payment proof, and receives the result.

Tool docs

Each tool has its own dedicated blog post with live playground. Browse the catalog above, then read individual deep-dives:

Live playground

Try the payment flow in your browser: x402.freeq.one/try.html — connect a wallet, pick a tool, pay USDC on Base, get results.

Part of the x402 Gateway — 21 tools, USDC micropayments on Base, powered by the x402 protocol.