## Overview

Three payment protocols let AI agents pay for API access. Each has different trade-offs:

| | [x402](/kb/x402) | [MPP](/kb/mpp) | [L402](/kb/l402) |
|---|---|---|---|
| **Network** | Base (Ethereum L2) | Tempo | Bitcoin Lightning |
| **Currency** | USDC | pathUSD | BTC (satoshis) |
| **Speed** | ~2 seconds | Sub-second | Milliseconds |
| **Fees** | Low (L2 gas) | Very low | Very low |
| **SDK** | @coinbase/x402-express | mppx | Custom (LND/CLN) |
| **Facilitator** | Coinbase | Tempo network | Lightning node |
| **Stablecoin** | Yes (USDC) | Yes (pathUSD) | No (BTC volatility) |

## When to use x402

**Best for:** Production services that want the broadest ecosystem support.

- Backed by Coinbase with official SDKs in TypeScript, Go, and Python
- USDC stablecoin means predictable pricing
- Base L2 keeps gas fees low
- Largest growing ecosystem of x402-enabled services
- Includes Bazaar discovery for service catalogs

## When to use MPP

**Best for:** High-frequency micropayments where speed matters.

- Sub-second finality on the Tempo chain
- Designed specifically for machine-to-machine payments
- pathUSD stablecoin (1:1 with USD)
- Simple SDK (mppx) with Express middleware
- Lowest overhead per transaction

## When to use L402

**Best for:** Bitcoin-native services and Lightning ecosystem integration.

- Instant settlement via Lightning Network
- No stablecoin — payments in satoshis (BTC)
- Macaroon-based auth tokens enable flexible access control
- Established ecosystem (since 2020, originally "LSAT")
- Requires running or connecting to a Lightning node

## Can I support multiple protocols?

Yes. agentgrade checks for all three independently. Supporting multiple protocols gives agents more payment options. The agent chooses which to use based on what wallets/funds it has available.

Publish all supported protocols in your `/.well-known/x402.json` service catalog so agents can discover them.

## Which should I start with?

If you're unsure, **start with x402**. It has the most complete SDK, Coinbase backing, and stablecoin pricing. Add MPP or L402 later if your use case benefits from their specific strengths.

## Related

- [OpenAPI](/kb/openapi)