A web search API your AI agent can pay for by itself

Most APIs assume a human: sign up, verify an email, paste a card, manage a key. An autonomous agent can't do any of that. Superhighway uses x402 — the open "HTTP 402 Payment Required" standard — so an agent pays per call with its own wallet, in one round-trip.

The whole flow is two HTTP requests

agent ── GET /search?q=...        ─▶  Superhighway
agent ◀─ 402 + payment terms      ──  (price, network, payTo, asset = USDC)
agent ── signs USDC payment, retries with X-PAYMENT ─▶
agent ◀─ 200 + results + settlement receipt

Try the first half yourself — an unpaid request returns the machine-readable terms:

curl "https://superhighway.walls.sh/search?q=hello"
# HTTP 402
# {"accepts":[{"scheme":"exact","network":"base","maxAmountRequired":"1000",
#   "asset":"0x833589...2913 (USDC)","payTo":"0xF7fd...E163", ...}]}

An x402 client library (for example x402-fetch or x402-axios in JavaScript) handles the second half automatically: it reads the 402, signs an EIP-3009 USDC authorization with the agent's wallet, and retries. Payment is gasless for the buyer — the agent needs USDC on Base, not ETH.

What it costs

No minimums, no subscription, no account. The machine-readable spec lives at /openapi.json and the agent-readable summary at /llms.txt.

Why this matters for agents

An agent that can clear a paywall by itself can pick up new tools mid-task — no human provisioning keys ahead of time. That is the whole bet behind x402: services describe their price in the protocol, agents carry wallets, and tool acquisition becomes a runtime decision instead of a deployment decision.

If a human is in the loop, the conventional lane exists too: a free API key (1,000 calls/month) with flat monthly plans above it. Same API, same results — two ways to pay.

Use it as an MCP tool instead

If your agent speaks MCP, skip the HTTP details entirely: one command adds all five tools and the server handles payment internally.