# Overview

Fast Skill is complete payment infrastructure designed for AI agents. Its payment stack consists of three integrated layers shown below:

```
                        FAST SKILL PAYMENT STACK

 +-----------------------------------+  +-------------------------------+
 |    Payment Protocol Adapters      |  |     Funding Abstraction       |
 |    Entity <-> Entity Agreement    |  |   Fiat <-> Crypto Agreement   |
 |                                   |  |                               |
 |  +-------+  +-------+  +-------+  |  |  +--------+ +-------+ +-----+ |
 |  | x402  |  |  ACP  |  |Stripe |  |  |  | Credit | |Stable-| |Bank | |
 |  +-------+  +-------+  +-------+  |  |  |  Card  | | coins | |Xfer | |
 |                                   |  |  +--------+ +-------+ +-----+ |
 +-----------------+-----------------+  +---------------+---------------+
                   |                                    |
                  API                            On/Off ramping
                   |                                    |
                   v                                    v
 +---------------------------------------------------------------------+
 |                                                                     |
 |                       Core SDK Execution                            |
 |                  Account <-> Account Agreement                      |
 |                                                                     |
 |   +---------------------+     +---------------------------+         |
 |   |      Fast SDK       |     |        AllSet SDK         |         |
 |   |   Fast <-> Fast     |     | Fast/Chain <-> Fast/Chain |         |
 |   +----------+----------+     +-------------+-------------+         |
 |              |                              |                       |
 |              v                              v                       |
 |   +-----------------------------------------------------+           |
 |   |                   FAST network                      |           |
 |   +-----------------------------------------------------+           |
 |                                                                     |
 +---------------------------------------------------------------------+

```

### Core SDK Execution

The foundation layer handles account-to-account operations on the Fast network:\
\
• Fast SDK — Native Fast-to-Fast transfers with sub-second settlement\
• AllSet SDK — Seamless movement between Fast and external networks (Base, Arbitrum, Ethereum, etc.) without bridging complexity

### Payment Protocol Adapters

Entity-to-entity payment protocols that standardize how agents request and send payments:\
\
• x402 — HTTP-native payment protocol (pay-per-API-call)\
• ACP — Agent Communication Protocol for agent-to-agent commerce\
• Stripe — Traditional payment rails integration

### Funding Abstraction

Simplifies how money enters and exits the system:\
\
• Credit card on-ramps\
• Stablecoin deposits\
• Bank transfers

The SDK exposes these layers through a unified API — you call `send()` or `receive()`, and Fast handles the routing, settlement, and cross-chain complexity underneath.