Engineering · March 2026

How We Built the First x402 Service Directory

archtools.dev · March 17, 2026 · 7 min read

The x402 protocol lets AI agents pay for API calls with crypto — no credit card, no subscription, no human in the loop. Coinbase built the protocol. Developers started building services. But nobody built the directory.

We just shipped it. The x402 Service Directory is the first comprehensive catalog of x402-enabled APIs — 64 tools across 15+ chains, searchable by category, network, and price. With a machine-readable API so your agents can discover services programmatically.

64
AI Tools Listed
15+
Chains Supported
6
Token Types
$0.001
Min Per Call

What x402 Is (and Why It Matters)

HTTP status code 402 Payment Required has existed since 1997. It sat unused for almost 30 years. Coinbase's x402 protocol finally gives it a purpose: a standardized way for servers to request payment and for clients — including AI agents — to pay, all within a single HTTP round-trip.

Here's the flow:

  1. Agent calls an API endpoint
  2. Server responds with 402 and a payment requirement (amount, token, network)
  3. Agent signs a crypto payment (USDC, USDT, ETH, SOL, etc.)
  4. Agent retries with a payment header — server verifies, executes, returns the result

No API keys. No accounts. No Stripe. Just a wallet with funds and a standard protocol.

x402 is to API payments what OAuth was to API authentication — a standard that makes everything interoperable.

The Problem: No Central Directory

x402 adoption is accelerating. Coinbase launched the x402 Bazaar. Developers are wrapping their APIs with @x402/express middleware. Agent frameworks like LangChain and CrewAI are adding x402 payment support.

But there's been no way for an agent to answer a simple question: "Which APIs accept x402, what do they cost, and which chains do they support?"

Every x402 service exposes /.well-known/x402 — but you need to know the URL first. There's no search. No catalog. No machine-readable index. An agent building a workflow has to hard-code every service URL it might need.

That's the problem we solved.

What We Built

The x402 Service Directory is a searchable catalog of every x402-enabled API we've cataloged. Here's what's in it:

For Developers (the UI)

Browse all 64 tools with filtering by category (AI, scraping, crypto, utilities), chain support, token type, and price range. Each listing shows endpoint, pricing, supported networks, and a direct link to test it in the x402 Playground.
For Agents (the API)

A machine-readable JSON endpoint at /api/v1/directory returns the full catalog. Your agent can query it, filter by capability, compare prices across providers, and build workflows dynamically — without any hard-coded service URLs.

The Directory API

# Fetch the full x402 service catalog
curl https://archtools.dev/api/v1/directory

# Response:
{
  "services": [
    {
      "name": "web-scrape",
      "category": "scraping",
      "description": "Extract content from any URL",
      "endpoint": "/v1/tools/web-scrape",
      "pricing": {
        "x402": { "amount": "0.001", "token": "USDC" },
        "credits": 3
      },
      "chains": ["base-mainnet", "ethereum-mainnet", "solana-mainnet", ...],
      "tokens": ["USDC", "USDT", "ETH", "SOL", "BNB"]
    },
    ...
  ],
  "total": 64,
  "updated": "2026-03-17T00:00:00Z"
}

# Filter by category
curl https://archtools.dev/api/v1/directory?category=ai

# Filter by chain
curl https://archtools.dev/api/v1/directory?chain=solana-mainnet

# Filter by price range (in USDC)
curl https://archtools.dev/api/v1/directory?max_price=0.005

The Full Stack

Beyond the directory, we shipped a complete x402 integration layer:

1. Coinbase x402 SDK Integration

Every one of our 64 tools accepts x402 payments using the official @x402/express SDK from Coinbase. The middleware handles payment verification, on-chain settlement, and receipt generation. We didn't roll our own — we use the standard.

2. Agent Wallet Funding Page

The funding page lets agent operators load USDC into their agent's wallet. Connect via WalletConnect, MetaMask, or Coinbase Wallet. Pick a network. Fund and go. Your agent can start calling APIs in minutes.

3. Interactive x402 Playground

The x402 Playground lets you test any tool with a real x402 payment. Pick a tool, connect a wallet, pay $0.001 in USDC, and watch the full round-trip: payment header construction, on-chain verification, tool execution, receipt. It's the fastest way to understand how x402 works.

4. Analytics Dashboard

The analytics dashboard shows real-time x402 payment volume, most-called tools, network distribution, and settlement stats. We built it for transparency — you can see exactly how the x402 ecosystem is growing on Arch Tools.

How We Handle Multi-Chain

Supporting 15+ chains isn't just about listing them. Each network has different settlement times, gas costs, and token availability. Here's how we handle it:

// Supported networks and their primary tokens
const SUPPORTED_CHAINS = {
  "base-mainnet":      ["USDC", "USDT", "ETH"],    // Primary — lowest fees
  "ethereum-mainnet":  ["USDC", "USDT", "ETH"],
  "solana-mainnet":    ["USDC", "SOL"],
  "bsc-mainnet":       ["USDT", "BNB"],
  "polygon-mainnet":   ["USDC", "USDT"],
  "arbitrum-mainnet":  ["USDC", "USDT", "ETH"],
  "optimism-mainnet":  ["USDC", "USDT", "ETH"],
  "avalanche-mainnet": ["USDC", "USDT"],
  "near-mainnet":      ["NEAR"],
  "bittensor-mainnet": ["TAO"],
  // + 5 more chains
};

// Agent picks the cheapest chain with available balance
function selectOptimalChain(agentWallet, requiredAmount) {
  return Object.entries(SUPPORTED_CHAINS)
    .filter(([chain]) => agentWallet.hasBalance(chain, requiredAmount))
    .sort((a, b) => getGasCost(a[0]) - getGasCost(b[0]))
    [0];
}

Base is the recommended default — it has the lowest fees and fastest settlement for USDC. But agents operating on Solana, BNB Chain, or any other supported network can pay natively without bridging.

How to List Your Service

The directory is open for submissions. If you've built an API that accepts x402 payments, we want to list it.

Submit Your x402 Service

Option 1: Open a PR on GitHub adding your service to the directory config.

Option 2: Fill out the submission form on the directory page.

Requirements: Your API must expose a valid /.well-known/x402 endpoint, accept at least one supported token, and return consistent responses. We verify every submission before listing.

Submission Format

// Add to directory-services.json
{
  "name": "your-service-name",
  "provider": "Your Company",
  "description": "What your API does in one sentence",
  "endpoint": "https://api.yourservice.com/v1/action",
  "wellKnown": "https://api.yourservice.com/.well-known/x402",
  "category": "ai | scraping | crypto | utilities | data",
  "pricing": {
    "amount": "0.001",
    "token": "USDC"
  },
  "chains": ["base-mainnet", "ethereum-mainnet"],
  "docs": "https://docs.yourservice.com"
}

What This Means for the Agent Economy

A directory isn't just a list. It's infrastructure. When agents can programmatically discover, compare, and pay for services — the agent economy starts to self-organize.

Today an agent building a research workflow has to be pre-configured with specific API URLs. With the directory API, that agent can:

  1. Query the directory for "scraping" services
  2. Compare prices across providers
  3. Pick the cheapest option on the chain where it holds funds
  4. Call the service, pay per use, get the result

No hard-coded URLs. No pre-negotiated contracts. No human approvals. Just autonomous service discovery and payment.

The first step toward an autonomous agent economy isn't better models — it's better infrastructure. Discovery + payment + execution in a single standard protocol.

Try It Now

Everything is live. No waitlist.

List your API in the directory.

The x402 Service Directory is open for submissions. If your API accepts x402 payments, it should be here.

Browse Directory → Try Playground