AI Agents & x402 Payments

Introduction

AI agents are becoming first-class consumers of on-chain services: reading ledger state, building transactions, and — increasingly — paying for the data and APIs they use. Radix is being positioned as a settlement layer for this agentic economy, combining asset-oriented programming, ROLA authentication, and the throughput of Hyperscale. This page collects the developer-facing pieces: the x402 payment standard, agent wallets, and the Model Context Protocol (MCP) tooling that lets coding and consumer agents work with Radix.

What is x402?

x402 is an open standard that activates the long-dormant HTTP 402 Payment Required status code as a real payment mechanism. A client — a browser, an app, or an AI agent — requests a resource; the server replies with a price; the client authorizes a stablecoin (or token) payment; the resource is delivered. One HTTP round-trip, with no accounts, subscriptions, or API keys. It was introduced by Coinbase in 2025 and is now stewarded by the x402 Foundation alongside Cloudflare, Google, and Visa.

A key role in the protocol is the facilitator, which abstracts blockchain complexity — fee handling, transaction submission, and network selection — while remaining non-custodial: the agent controls what is paid, the facilitator handles how it settles. This separation is what makes x402 usable by clients with no blockchain knowledge.

Why Radix for Agentic Payments

Agentic commerce is fundamentally a high-volume micropayment problem: millions of small, machine-to-machine payments for content, compute, and API calls. That workload only settles on a ledger that can scale horizontally without sacrificing atomic composability — which is the explicit goal of Hyperscale (Xi’an), where shards reconfigure with usage so capacity follows demand.

Beyond raw throughput, Radix brings primitives that suit programmable agent payments: native asset-oriented resources, transaction manifests that make intent explicit, and subintents for partial, multi-party flows. Builders should note the trade-offs surfaced during Hyperscale testing — subintents currently cost roughly 2× a plain transfer and hit the 256-event limit at around 30 subintents per transaction (versus 127 plain transfers) — so high-frequency micropayments generally need to be bundled.

Building x402 on Radix

The x402 reference implementation is multi-chain and split into composable packages, with middleware for common server frameworks:

• x402 (implementation) — the protocol repo, with a TypeScript SDK (@x402/core, plus framework adapters such as @x402/express, @x402/hono, @x402/next, and @x402/fetch) and chain implementations. Radix support is in active development.

• x402 Protocol Spec — the wire format and payment flow.

• Coinbase x402 Docs — the original reference documentation.

• radix-web3.js — an Effect-native TypeScript toolkit useful for constructing and submitting the Radix transactions an x402 facilitator settles.

A minimal x402 server gates a route behind a payment requirement:

app.use(paymentMiddleware({
  "GET /weather": {
    accepts: [/* networks / schemes you support */],
    description: "Weather data",
  },
}));

AI Agent Tooling on Radix

A growing toolset lets AI agents read Radix, build transactions, and act on a user's behalf:

• RadixScan Agent Layer — a keyless MCP server (mcp.ai.radixscan.io) that lets agents read the ledger and build, validate, and simulate manifests, then request a signature non-custodially (the server holds no keys; signing happens in the user's wallet). Transports: /mcp (HTTP) and /sse.

• Awesome Radix MCP Servers — a curated index of MCP servers in the Radix ecosystem.

• Radix Context for AI Agents — 19 curated context files (radix-context) that teach coding agents how to build on Radix.

• Radix Skills — installable agent skills for Radix dApp, manifest, Scrypto, and Gateway work (skills.sh).

• AI Agent Wallet — an open-source, natural-language wallet SDK for agents that can interact with Radix DEXs, lending (WEFT), and staking.

To connect an MCP-capable coding agent (e.g. Claude Code) to the RadixScan server, add it to your project's .mcp.json:

{
  "mcpServers": {
    "radixscan": {
      "type": "http",
      "url": "https://mcp.ai.radixscan.io/mcp"
    }
  }
}

External Links

• x402 — Internet-Native Payments Standard
• Coinbase x402 Documentation
• x402 implementation — GitHub
• RadixScan Agent Layer
• Awesome Radix MCP Servers
• Radix Skills