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Starter kit $49

Monetize your API with x402

Charge AI agents per call in USDC on Base. We run 53 paid endpoints in production; the $49.00 starter kit is that server as a zip, the $0.25 audit lints your live 402, and the white-label pack deploys the whole stack under your brand and payTo.

$49.00starter kit · USDC on Base · one-time
Starter kit Audit my endpoint White-label

01 / Field notes

What breaks x402 sales (from our own logs)

Each of these cost us real sales before we fixed it. The audit checks for all of them.

  1. 01

    Keep the payment description at 500 characters or less. Coinbase CDP rejects a longer resource.description at verify and settle, while its validator still says valid.

  2. 02

    Keep the 402 response headers under 16 KB. Node's fetch (undici, used by every @x402/fetch buyer) fails on larger headers that curl reads fine. A big example in the Bazaar extension is the usual cause.

  3. 03

    Stay under the $1 default. Default x402 buyers refuse a single payment above $1, so a $49 product needs the buyer to raise maxAmountPerPayment, and the page must say so.

  4. 04

    Never 402 a method your OpenAPI does not declare. Directory crawlers probe every method on the template URL and read an undeclared 402 as a missing input schema.

  5. 05

    Validate before you challenge. A buyer who signs for garbage input and then gets a 400 does not come back. Answer bad input with 400 before the 402.

  6. 06

    Settle only after success. Hold the body until the settle succeeds, never charge a 4xx or 5xx, and give every paid answer a free status URL.

02 / Offers

Pick your rung

For teams selling to agents
OfferUSDC
GET /v1/base/x402-starter-kitx402 Paid-API Starter Kit (zip, $49.00 USDC)$49.00
GET /v1/x402/auditx402 Seller Audit lint ($0.25): score + fix list for any 402 endpoint$0.25
GET /v1/x402/audit/fullx402 Seller Audit full ($2.00): lint + CDP validator + Bazaar index + discovery$2.00
GET /v1/base/research-rails-retainerResearch + Rails Retainer (1 month) ($999.00 USDC)$999.00
GET /v1/base/white-label-rails-packWhite-Label x402 Rails Pack ($2,500.00 USDC)$2,500.00

03 / Audit

Lint any 402 for $0.25

Read-only, never pays your endpoint. Decodes the live 402 (v1 body or v2 header), checks accepts[], header size, description length, the $1 cap, the Bazaar schema and CORS, then returns a 0-100 score and a fix list.

Request (quote is free)
curl -i 'https://agents.avasis.ai/v1/x402/audit?url=https%3A%2F%2Fyour-api.example%2Fv1%2Fpaid-route'
# free docs
curl https://agents.avasis.ai/v1/x402/audit/info

04 / Questions

Questions builders ask

  1. Q1

    What is x402?
    An open HTTP payment standard: the server answers 402 Payment Required with a machine-readable price, the client pays (USDC on Base here, through a facilitator such as Coinbase CDP) and repeats the request. No accounts or API keys.

  2. Q2

    Do I need my own wallet?
    Yes. You keep your own payTo address; the kit and the white-label pack never route your revenue through Avasis.

  3. Q3

    How do agents find my API?
    Publish /.well-known/x402, openapi.json with x-payment-info, and llms.txt, then register on x402scan and the CDP Bazaar (indexed after your first settle). The starter kit ships example files and DIRECTORIES.md.