Pay-per-call APIs for AI agents: 22 tools, no API key, from $0.003

Last updated: 2026-10-14

What a pay-per-call API is

A pay-per-call API is an HTTP API you pay for one request at a time, with no account, API key or subscription. On grokzilla.shop an AI agent sends a normal POST, gets HTTP 402 with the price, pays in USDC on Base with x402 v2, and retries the same request to get its JSON result.

How payment works

POST the JSON body to the skill endpoint with no payment header.
The server answers HTTP 402 with a PAYMENT-REQUIRED header: x402 v2, scheme exact, network eip155:8453, asset USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, payTo 0xc22f9CAEBAc37fE72D5142f35f21f6696Ea9Ef69.
Sign the exact USDC amount with any x402 v2 client and retry with the PAYMENT-SIGNATURE header.

Your first call: uuid-mint for $0.003

curl (shows the 402 and its terms):

curl -i -X POST https://grokzilla.shop/api/skills/uuid-mint \
  -H 'Content-Type: application/json' -d '{"count":1,"version":4}'

JavaScript: wrap fetch with the @x402/fetch package and a Base wallet signer; it reads the 402, pays and retries the same POST for you (see its README for the current setup).

Python (read the 402 terms, then pay with your x402 v2 client):

import requests
r = requests.post("https://grokzilla.shop/api/skills/uuid-mint", json={"count": 1, "version": 4})
print(r.status_code, r.headers.get("PAYMENT-REQUIRED"))  # 402 + base64 payment terms

The catalog

Skill	Endpoint	Price per call (USD)
Public OSINT Graph	`POST /api/skills/osint-graph`	$0.01
Deep Research	`POST /api/skills/research`	$0.015
SEO Optimizer	`POST /api/skills/seo`	$0.012
AI Content Detector	`POST /api/skills/ai-detector`	$0.01
JSON Flattener	`POST /api/skills/json-flatten`	$0.006
JSON Key Sorter	`POST /api/skills/json-sort`	$0.003
Text Diff	`POST /api/skills/text-diff`	$0.006
URL Normalizer	`POST /api/skills/url-normalize`	$0.005
HTML Cleaner	`POST /api/skills/html-clean`	$0.008
JSON Schema Validator	`POST /api/skills/json-schema-validate`	$0.006
Keyword Extractor	`POST /api/skills/keyword-extract`	$0.008
Token Counter	`POST /api/skills/token-count`	$0.004
NICJE Data Refinery	`POST /api/skills/nicje`	$0.02
SHA-256 Hash	`POST /api/skills/sha256`	$0.003
UUID Minter	`POST /api/skills/uuid-mint`	$0.003
Slugify	`POST /api/skills/slugify`	$0.003
PII Redactor	`POST /api/skills/pii-redact`	$0.003
CSV Normalizer	`POST /api/skills/csv-normalize`	$0.003
Base64 Encode/Decode	`POST /api/skills/base64`	$0.003
Epoch Converter	`POST /api/skills/epoch-convert`	$0.003
URL to Markdown	`POST /api/skills/url-to-markdown`	$0.003
Token Risk (Base)	`POST /api/skills/token-risk`	$0.005

Discovery for agents

/.well-known/x402 (manifest)
/api/catalog (prices, schemas, examples)
/openapi.json
/llms.txt and /llms-full.txt
/AGENTS.md

Humans: paying with Stripe

No wallet? Pick a skill on /try or see /pricing to pay by card through Stripe checkout. Terms: /terms.

FAQ

Do I need an account or API key?

No. Every paid route answers an unpaid POST with HTTP 402 and the payment terms; any x402 v2 client can pay and retry. There is no signup.

Which network and asset?

USDC on Base mainnet (eip155:8453), x402 v2 with the exact scheme.

What does a call cost?

Between $0.003 and $0.02 per call, listed per skill in the table on this page, at /pricing and in /api/catalog.

Is there a free tier?

No. Free beta is off; every skill call is paid. The discovery files (catalog, manifest, OpenAPI, llms.txt) are free to read.

Does the server accept x402 v1?

No. The server is x402 v2 only; a v1 payment header gets a 402 back with the v2 terms.

Can humans pay without a crypto wallet?

Yes, through Stripe checkout on the site (see /pricing for the minimum).