Turnstile series
Building a paid lane for onchain data agents: a seller agent that answers Uniswap pool questions over x402, built over ETHOnline 2026. Payments, discovery, identity, spending limits and the data behind the answer, one post each.
Part 1Oct 5, 202619 minx402 on Hedera: what a paid HTTP request is made of
A seven-cent API call settled through Blocky402: the 402 challenge, a transfer the buyer signs but cannot send, a facilitator that pays the gas, a replay guard, and a receipt anyone can read back.
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Part 2Oct 6, 202617 minGasless nanopayments on Arc, and the nonce that stays at 0
An AI agent paid for eleven queries without ever sending a transaction. How EIP-3009 authorizations and Circle Gateway batching make that work, and who pays for what.
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Part 3Oct 7, 202615 minOne payment interface, four chains
A four-method PaymentRail interface, a registry that turns rails into accepts[], a test that fails the build when a chain name leaks into the service, two Base interop surprises, and selling through a gateway that collects the payment for you.
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Part 4Oct 8, 202617 min197 ERC-8004 agents, and where their prices live
We indexed real ERC-8004 agent registrations on Base, Ethereum mainnet and Sepolia with Substreams, The Graph's block-streaming indexer, using one Rust module for all three chains. The registry tells you who exists. What they cost is somewhere else.
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Part 5Oct 9, 202614 minThe offer is the name: ENSv2 records and a key split the chain enforces
How Turnstile publishes a seller's price, payment rails and endpoint as ENSIP-25/26 resolver records, lets a hot key change only the price and the MCP endpoint using ENS's Enhanced Access Control, and uses fork tests to prove that key can't redirect the payout. The split limits what each key can do.
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