Frequently asked questions
What Pony is, what a plan buys, and how a program with a wallet gets one without a human in the way.
What is Pony?
A transactional email API. You send one HTTP request with a sender, a recipient, a subject and a body, and Pony delivers it and tells you what happened to it. It is built for the messages an application sends by itself — receipts, password resets, alerts — rather than for newsletters or campaigns.
How does an AI agent buy a plan without a human?
It calls the API with no credentials and gets back 402 Payment Required with a PAYMENT-REQUIRED header. That header is a base64 x402 document naming every plan on sale and, for each, the exact amount, token, chain and destination address. The agent signs one EIP-3009 USDC authorisation for the plan it chose and posts it to that plan's purchase route. The response carries an API key, the plan, the sends included, the expiry and a working sending address. Retrying the original send with that key succeeds.
What does a plan include?
Pro is 50,000 emails every 30 days with no daily cap, for 19.00 USDC. Scale is 100,000 emails every 30 days with no daily cap, for 79.00 USDC. Both include the full API, webhooks and message logs. A plan is a fixed 30-day window rather than a calendar month, so a year is about 12.2 windows rather than 12.
What happens when I run out of sends?
The next send answers 402 with a fresh quote you can pay. Nothing renews on its own and nothing bills you for going over, so there is no overage invoice and no surprise. An expired plan behaves the same way as an exhausted one.
Is there a free plan?
Not yet. A free tier of 3,000 emails every 30 days, capped at 100 a day, is defined in the catalogue but is neither sold nor granted today, so the two plans you can actually obtain are Pro and Scale.
Which SDK should I install?
None, because there are none. Pony publishes the integration itself rather than a client per language: a plain text file at /llms.txt, a Claude skill, tool schemas for OpenAI and Gemini, and an MCP server. Read one and write the client in whatever language you are already using.
Do I need to set up DNS before I can send?
Not for the first send. A purchase provisions a verified sending identity on a subdomain Pony controls, and it works immediately. That identity carries a volume ceiling, so sending at real volume means adding a domain you own and publishing the four DNS records the API returns.
How do delivery events reach my application?
Register an endpoint and Pony posts signed events to it: delivered, bounced, complained, opened and rejected. The signature is an HMAC-SHA256 over the payload with a timestamp. Delivery is at-least-once with a dead-letter queue, so deduplicate on the delivery id header rather than assuming each event arrives once.
What does Pony deliberately not do?
Attachments, open and click tracking, templates, contact lists and audiences. It is a transactional send API only. If you need a campaign tool, this is the wrong product.
What am I actually paying with?
USDC on Base. Settlement goes through an x402 facilitator, so Pony never holds a key, never verifies a signature, and cannot alter the amount or the recipient — both are inside the authorisation you signed.
The whole purchase exchange, quoted from the API’s own test fixtures, is on the page for agents. Every endpoint, error name and header is in the API documentation. What a plan costs is on the pricing section, and what happens if you want your money back is in the refund policy.