# Overview

> Gate an HTTP service for stablecoin payments — with the pay CLI (no code) or a language SDK (in-process). When to use which, and what each SDK supports.

There are two ways to add stablecoin payment gating to an HTTP service:

- the **`pay` CLI** — declare your endpoints and pricing in a YAML spec and run a gateway, no code; or
- a **language SDK** — gate routes inside your own server process, when you need deeper integration.

Both speak the same `402 Payment Required` handshake (MPP and x402) and the same gate model — an amount, the protocols you accept, and optional fees — so you can move from one to the other (or run both) without changing the payment model.

## Start with the CLI

For most APIs the CLI is the fastest path and needs no code. Point it at a [provider YAML](/docs/building-with-pay/yaml-specification) and it runs a gateway that issues 402 challenges, verifies and settles payments, and (optionally) proxies paid requests to your upstream:

```sh
pay server start provider.yml
```

The YAML declares routing, pricing and metering, subscriptions, and payment splits — see [Building with pay](/docs/building-with-pay). Reach for the CLI when you're gating an existing or upstream API, want the pay-skills catalog and discovery, or simply don't want payment logic in your application code.

## Reach for an SDK when you need deeper integration

An SDK gates routes **inside your application process**, so you can:

- price or meter a request from your own app state — tokens generated, bytes served, rows returned;
- run logic in the paid handler and read the verified payment;
- embed gating in your existing framework's middleware;
- act as a **paying client**, not just a server.

<Callout type="info">
  The CLI and the SDKs are the same engine: a gate is an amount plus the protocols it accepts, settled over MPP or x402.
  Choosing an SDK doesn't change the wire protocol — it just moves the gate into your code.
</Callout>

## The SDKs

| Language   | Package                                   | Frameworks                                  | Guide                                |
| ---------- | ----------------------------------------- | ------------------------------------------- | ------------------------------------ |
| TypeScript | `@solana/pay-kit`                         | Express, Hono, Fetch (Workers / Next / Bun) | [TypeScript →](/docs/sdk/typescript) |
| Rust       | `solana-pay-kit`                          | axum                                        | [Rust →](/docs/sdk/rust)             |
| Go         | `github.com/solana-foundation/pay-kit/go` | net/http                                    | [Go →](/docs/sdk/go)                 |
| Python     | `solana-pay-kit`                          | FastAPI, Flask, Django                      | [Python →](/docs/sdk/python)         |

Every SDK ships a paying client of some form; **TypeScript is the reference surface and the most complete.**

### Scheme support

Which payment schemes each SDK exposes as a one-line gate today. Where a cell is `—`, the protocol is often still reachable through that SDK's lower-level protocol layer — see the per-language guide.

| Scheme           | TypeScript | Rust | Go  | Python |
| ---------------- | :--------: | :--: | :-: | :----: |
| Fixed charge     |     ✅     |  ✅  | ✅  |   ✅   |
| Usage (`upto`)   |     ✅     |  ✅  | ✅  |   ✅   |
| Session          |     ✅     |  —   |  —  |   ✅   |
| Subscription     |     ✅     |  —   |  —  |   —    |
| Batch-settlement |     —      |  ✅  |  —  |   —    |

## Next

- [Building with pay](/docs/building-with-pay) — the CLI + YAML path, end to end.
- [Toolchain](/docs/toolchain) — the full `pay` CLI reference.
- Per-language guides: [TypeScript](/docs/sdk/typescript), [Rust](/docs/sdk/rust), [Go](/docs/sdk/go), [Python](/docs/sdk/python).