# Payment Protocol Adapters

Payment Protocol Adapters define *how* payments are requested and executed between entities — whether that's an agent paying for an API call, a service charging for compute, or two agents transacting with each other.\
\
These adapters sit above the core SDKs and handle the negotiation layer: "I want this resource, here's my payment, verify and deliver."

### x402-sdk

Packages:\
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• `@fastxyz/x402-client` — For buyers/agents making payments\
• `@fastxyz/x402-server` — For merchants/services receiving payments\
• `@fastxyz/x402-facilitator` — For verifying and settling payments

HTTP-native payment protocol based on the `402 Payment Required` status code. Your agent requests a resource, the server responds with payment requirements, the agent pays, and gets access — all in a single HTTP flow.

Use cases:\
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• Pay-per-API-call (micropayments for AI services)\
• Gated content or compute access\
• Agent-to-agent commerce

> *More protocol adapters coming soon: ACP (Agent Communication Protocol), Stripe integration, and others.*


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