# Welcome to Fast Fast is payment infrastructure for programmatic transactions. It enables agents, APIs, merchants, and services to request, authorize, send, and settle payments — fully programmatically, across both crypto and fiat rails. Fast Skill is our main product that helps AI agents to build services and track businesses. Fast Skill bundles all the above features and functionalities as a complete set of SDKs for handling all settlement, signing, and network interaction automatically. Using Fast Skill, sending a payment is as easy as a function call that returns a receipt. *** ### Who Fast Is For #### AI and Automation Developers You build AI agents, autonomous workflows, or multi-agent systems. Your agents need to pay for resources — data, compute, storage, other agents' services — and receive payment for their own work. All of this must happen programmatically, without a human approving each transaction. With Fast, every agent has a wallet. Agents pay each other directly. Balances update in real time. An agent can earn, spend, and manage its finances autonomously. Install the SDK, create a signer, and submit payments with a single function call. See the [Fast SDK on GitHub](https://github.com/fastxyz/fast-sdk) for installation and code examples. #### API Developers You build APIs, services, or SaaS products. You want to monetize them with usage-based pricing — per request, per inference, per compute step, per action — without the overhead of subscriptions, API key management, billing systems, or invoice reconciliation. With Fast, your API charges the caller at the moment of use. Payment is part of the request-response cycle. No billing infrastructure required. Use the x402 middleware to protect routes and the x402 client to pay for resources — see the [x402 packages in the Fast SDK repo](https://github.com/fastxyz/fast-sdk) for integration examples. ### When to Use Fast Use Fast for **programmatic payments**, i.e., payments that block task execution or service response. Common scenarios include: * An API charging **$0.01 per request** * An agent paying another agent for a task * A service charging per compute, inference, or workflow step * An application charging per action instead of subscriptions * A merchant accepting payment from a software client or automated agent These patterns commonly appear in systems such as: * **Pay-per-use APIs** — monetize endpoints with per-request pricing * **Agent marketplaces** — agents discover, negotiate, and pay for services * **Automated service payments** — workflows pay for compute, data, or storage * **Machine-to-machine commerce** — software systems transact with each other and with merchants Fast supports multiple settlement assets based on needs: **Fiat** Supported fiat rails allow software systems to transact with real-world businesses and traditional services — without requiring the counterparty to hold or understand crypto. > Example: Agent pays **$5 USD** to complete a booking or purchase. **Stablecoins** Stablecoins are commonly used for digital services and micropayments because they provide predictable pricing with instant, programmable settlement. > Example: Agent pays **$0.01 USDC** for a single API request. Fast handles both settlement paths. Developers choose the settlement asset when creating a payment request — the payment lifecycle, authorization flow, and developer experience remain identical regardless of settlement method. ### Why Fast And Why Now As software systems increasingly perform economic activity — calling APIs, coordinating services, purchasing compute — payments must become part of the execution flow of software, not a manual step outside it. However, none of the current payment infrastructure is ready. Traditional payment rails require human authorization and batch in hours. Crypto payment systems offer programmability but cannot settle in fiat. Neither was built for machine-initiated transactions at scale. Fast's payment infrastructure is powered by a purpose-built settlement network engineered specifically for high-frequency programmatic payments. Three properties make this viable: #### Near-zero fees → Micropayments work. An agent can pay $0.001 per API call, $0.01 per inference, or $0.50 per task without transaction fees consuming the payment. This is what makes pay-per-request pricing viable for APIs and pay-per-action economics viable for agents. #### Sub-second finality → Agents don't wait. Payments settle in under one second and are immediately final — no pending states, no confirmation delays, no rollbacks. An agent does not wait. A workflow does not poll. The payment settles, the balance updates, and execution continues. #### Mathematical verification → When settling $1B/day, every tx is provably correct. Every transaction is provably correct. When infrastructure settles billions of dollars per day across millions of autonomous agents, correctness is not a feature. It is a requirement. *** ### How Fast Works Fast has several layers. Most developers only touch the first and the second. #### Compatibility Matrix | Packages\Fast | Release20260319 | Release20260407 | | ------------------------------------------------------------------------------------ | --------------- | --------------- | | [@fastxyz/schema](https://www.npmjs.com/package/@fastxyz/schema) | 1.0.0\~1.0.1 | 2.0.0 | | [@fastxyz/sdk](https://www.npmjs.com/package/@fastxyz/sdk) | 1.0.0\~1.0.1 | 2.0.0 | | [@fastxyz/allset-sdk](https://www.npmjs.com/package/@fastxyz/allset-sdk) | 1.0.0\~1.0.1 | 1.0.2 | | [@fastxyz/x402-client](https://www.npmjs.com/package/@fastxyz/x402-client) | 1.0.0\~1.0.2 | 1.0.3 | | [@fastxyz/x402-facilitator](https://www.npmjs.com/package/@fastxyz/x402-facilitator) | 1.0.0\~1.0.2 | 1.0.3 | | [@fastxyz/x402-server](https://www.npmjs.com/package/@fastxyz/x402-server) | 1.0.0 | 1.0.1 | | [@fastxyz/x402-types](https://www.npmjs.com/package/@fastxyz/x402-types) | 1.0.0 | 1.0.1 | | [@fastxyz/cli](https://www.npmjs.com/package/@fastxyz/cli) | 1.0.0\~1.0.1 | 1.0.2 | #### 1. Fast Skill Fast SDK is the developer-facing interface, but actually it is a wrapper around the Fast SDK. #### 2. Fast CLI A command-line tool for the Fast network — manage accounts, send USDC, bridge tokens between EVM chains and Fast, fund via fiat, and pay x402-protected APIs. #### 3. Fast SDK TypeScript SDK for the Fast network. Provides a high-level API for signing transactions, querying the network, and converting addresses and amounts. #### 4. AllSet Layer AllSet is the interchange layer wrapped around by the Fast Skill that connects Fast to both fiat and cryptos. AllSet enables agents to receive funds from any supported network and withdraw to any supported settlement destination. Fast Skill handles this automatically — developers do not need to interact with AllSet directly. #### 5. Fast Network Fast Network is the underlying settlement network that powers the Fast Skill. It enables massively parallel transaction processing and settlement, with no blocks, no consensus, and no validator-to-validator communication. This is what delivers sub-second finality, near-zero fees, and mathematically verified correctness. Developers never interact with this layer — it is the engine inside the car. *** ### Start Building Walk through the following materials to learn how to build with Fast step by step. | [**Quickstart**](https://github.com/Pi-Squared-Inc/GitBookDocs/blob/main/get-started/quickstart.md) | Get running in under 2 minutes | | --------------------------------------------------------------------------------------------------- | --------------------------------------- | | [**SDK References**](/sdk-references/overview.md) | Fast Skill's complete SDK documentation | | [**FAQ**](/faq.md) | Frequently Asked Questions about Fast | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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