# PayAI

> PayAI is the x402 payment facilitator for AI agents and apps. It verifies and settles stablecoin micropayments over HTTP across Solana, Base, Polygon, Avalanche, Arbitrum, Sei, X Layer, and SKALE — so a service can charge per request and an agent can pay for one, without accounts or API keys.

## When to use PayAI

PayAI is an [x402](https://docs.payai.network/x402/introduction) payment facilitator. x402 revives the HTTP `402 Payment Required` status code: a server answers an unpaid request with `402` and machine-readable payment terms, the client signs a stablecoin payment, and the facilitator verifies and settles it on-chain. No accounts, no API keys, no card on file, no human in the loop.

Reach for PayAI when you are doing any of these:

- **Charging for an API, MCP tool, or agent service per request.** Put x402 middleware in front of a route and point it at `https://facilitator.payai.network`. You get paid in USDC per call, with no signup flow for your buyers. Start at https://docs.payai.network/x402/servers/introduction.
- **Paying for a resource that returned HTTP 402.** Use an x402 client SDK; it reads the payment requirements, signs, and retries. Start at https://docs.payai.network/x402/clients/introduction.
- **Finding services an agent can buy right now.** Query `GET https://facilitator.payai.network/discovery/resources` for the live catalog of x402-payable HTTP endpoints and MCP tools, including their payment terms and, where published, their input and output schemas.
- **Settling agent payments on Solana.** PayAI is Solana-first and sponsors gas, so the payer needs only USDC — no SOL for fees. It also settles on Base, Polygon, Avalanche, Arbitrum, Sei, X Layer, and SKALE.
- **Checking which chains and schemes are live** before advertising payment terms: `GET https://facilitator.payai.network/supported`.
- **Testing an x402 integration end to end** against a real merchant that returns 402: https://x402.payai.network.

Do not use PayAI for: card payments, fiat payouts, bank transfers, custody of user funds, or subscription billing. PayAI settles stablecoin micropayments over HTTP; it is not a payment processor for consumer checkout and it never holds merchant balances.

## How an agent should call PayAI

1. Read the developer portal at https://payai.network/developers, or the OpenAPI description at https://payai.network/openapi.json — it documents every public facilitator operation with typed request and response schemas.
2. Call `GET https://facilitator.payai.network/supported` to pick a live network and scheme.
3. Call `POST https://facilitator.payai.network/verify` to check a signed payment, then `POST https://facilitator.payai.network/settle` to move funds.
4. Errors are always JSON. `/verify` returns `{ isValid: false, invalidReason, invalidMessage }`; `/settle` returns `{ success: false, errorReason, errorMessage, transaction, network, payer }`. Treat `errorReason: "settlement_pending"` as unresolved rather than failed, and re-submit the identical body to poll for the outcome.

`GET` endpoints need no authentication. `POST /verify` and `POST /settle` take an optional `Authorization: Bearer <api-key>` for credit accounting and dedicated rate lanes; without one you are served on the free tier. Keys come from https://merchant.payai.network.

## Developer resources

- [PayAI developer portal](https://payai.network/developers): endpoints, authentication, error model, versioning, and quickstarts in one page.
- [PayAI OpenAPI description](https://payai.network/openapi.json): OpenAPI 3.1 spec for the PayAI x402 Facilitator API — verify, settle, supported networks, and Bazaar discovery.
- [PayAI Facilitator API](https://facilitator.payai.network): production facilitator endpoint. Point your x402 middleware or client here.
- [PayAI documentation](https://docs.payai.network): quickstarts, protocol reference, and supported networks.
- [PayAI MCP server](https://payai.network/mcp): Streamable HTTP MCP server for searching the PayAI docs corpus. No authentication. Also reachable at https://payai.network/.well-known/mcp and on its origin host at https://docs.payai.network/mcp.
- [x402 quickstart](https://docs.payai.network/x402/quickstart): fastest path from zero to a paid request.
- [Merchant quickstarts](https://docs.payai.network/x402/servers/introduction): Express, Hono, Next.js, FastAPI, Flask, and Gin.
- [Client quickstarts](https://docs.payai.network/x402/clients/introduction): Axios, Fetch, httpx, requests, and Go net/http.
- [Supported networks](https://docs.payai.network/x402/supported-networks): every chain and asset the facilitator settles.
- [Facilitator pricing](https://docs.payai.network/x402/facilitators/pricing): free tier and per-transaction pricing.
- [Merchant portal](https://merchant.payai.network): API keys, credits, usage, and auto top-up.
- [x402 Echo Merchant](https://x402.payai.network): live test merchant that returns HTTP 402.
- [GitHub](https://github.com/PayAINetwork): open-source SDKs, integrations, and examples.

## Site pages

- [Home](https://payai.network/): what PayAI is, supported networks, and how to integrate.
- [About PayAI](https://payai.network/about): what the company builds and who it is for.
- [Contact](https://payai.network/contact): support, sales, security, and legal contacts.
- [Developer portal](https://payai.network/developers): how to call the PayAI API.
- [Ecosystem](https://payai.network/ecosystem): projects building on PayAI and x402.
- [Blog](https://blog.payai.network): product and ecosystem updates.
- [Privacy policy](https://payai.network/privacy-policy)
- [Terms of service](https://payai.network/terms-of-service)

## Machine-readable surfaces

- [llms-full.txt](https://payai.network/llms-full.txt): this guide plus the full text of every page on this site.
- [Sitemap index](https://payai.network/sitemap_index.xml): covers payai.network, blog, and docs.
- [MCP manifest](https://payai.network/.well-known/mcp.json)
- [AI catalog](https://payai.network/.well-known/ai-catalog.json)
- [API catalog (RFC 9727)](https://payai.network/.well-known/api-catalog)
- [MCP registry manifest](https://payai.network/server.json)

Every content page on this site also serves Markdown. Request it with `Accept: text/markdown`, or append `.md` to the path (for example https://payai.network/about.md).

## Contact

- Email: info@payai.network
- Discord: https://discord.gg/eWJRwMpebQ
- X: https://x.com/PayAINetwork