Getting Started • 3 min read

Welcome to FareSide

x402 infrastructure: open-source tools and managed services for AI agent payments

FareSide is an x402 infrastructure project. We build open-source tools and managed services for the x402 protocol — the payment standard that lets AI agents pay for services autonomously.

What we offer:

  • x402-rs — Open-source Rust implementation (facilitator, middleware, client)
  • Hosted Facilitator — Production-ready payment verification and settlement
  • Advanced Features — Payment splits, cross-chain settlement, discovery (coming soon)

What is x402?

The x402 protocol is an open payment standard that enables machine-to-machine payments using HTTP status code 402 Payment Required. It allows:

  • API monetization — Charge per request without accounts or API keys
  • AI agent payments — Agents autonomously pay for services they need
  • Micropayments — Sub-cent transactions that aren’t viable with traditional payments
  • Better human UX — No accounts, no forms—just approve and pay
  • Extensible protocol — Supports human-sized payments and even card payments through protocol extensions

What is a Facilitator?

When accepting x402 payments, your service is responsible for landing the user’s transaction onchain to receive funds. You can handle this directly within your service, or offload it to a specialized 3rd party. The x402 protocol standardizes this role as a facilitator.

A facilitator:

  • Verifies payments — Confirms that client payment payloads meet your declared requirements
  • Settles payments — Submits validated payments to the blockchain on your behalf
  • Returns results — Provides verification and settlement responses so your code can decide whether to fulfill the request

The facilitator never holds funds or acts as a custodian — it only executes onchain transactions based on signed payloads provided by clients.

You can self-host a facilitator for full control, but it comes with operational burden: maintaining blockchain connectivity, managing nonces and gas prices, handling RPC reliability, and ensuring correct protocol behavior. Using a hosted facilitator like FareSide lets you skip all that.

Why FareSide?

Production-Proven Infrastructure

FareSide is built on x402-rs, our open-source Rust implementation that served up to 77% of global x402 transactions during peak usage. We’ve learned what works at scale and built infrastructure that handles it.

Reliable Settlement

Our proprietary (for now) transaction relayer goes beyond vanilla blockchain libraries:

  • Smart nonce management that doesn’t break under load
  • Automatic gas bumping for stuck transactions
  • Support for eth_sendRawTransactionSync (EIP-7966) for lower latency
  • Multi-RPC failover for reliability

Multi-Chain Acceptance

Accept payments on the chains your users prefer. Users pay where convenient, you accumulate where profitable:

  • Base
  • Solana
  • Polygon
  • Avalanche
  • Sei
  • XDC
  • X-Layer
  • …and more

Open Protocol, No Lock-in

FareSide implements the standard x402 protocol. Your integration works with any x402-compatible client, and you can self-host using x402-rs if you prefer.

How It Works

sequenceDiagram
    participant Buyer as Agent (Buyer)
    participant Seller as Service (Seller)
    participant Facilitator as FareSide Facilitator

    Buyer->>Seller: 1. Request resource
    Seller-->>Buyer: 2. 402 Payment Required
    Note over Buyer: 3. Create & sign payment voucher
    Buyer->>Seller: 4. Retry request with payment attached
    Seller->>Facilitator: 5. Verify payment
    Facilitator-->>Seller: 6. Payment valid
    Note over Seller: 7. Do the work
    Seller->>Facilitator: 8. Settle payment
    Facilitator-->>Seller: 9. Settlement confirmed
    Seller-->>Buyer: 10. Return result

Getting Started

  1. Join the Waitlist - Get your API key for the hosted facilitator
  2. Quickstart - Accept your first payment in 5 minutes
  3. x402 Protocol - Understand how the protocol works

Coming Soon

We’re building additional features for production use cases:

  • Payment Splits — Same-chain revenue sharing and multi-party payments
  • Multi-Chain Dashboard — View balances across chains, one-click consolidation
  • Discovery Service — Help AI agents find your services

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