Blog · series · 9 parts
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.
Turnstile: a market where AI agents pay per query
Agents that find a data seller through ENS, read its price on chain, pay per query over x402 and spend inside a mandate they cannot widen. Overview of the nine-part series.
x402 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.
Gasless 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.
One 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.
A sample of 197 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.
The 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.
Three listings per human: capping an open agent registry with World ID Selfie Check
How a Selfie Check caps Turnstile's open agent registry at three listings per human.
Spending mandates for agents: the wallet can never raise its own limit
How to give agents a money cap they cannot touch: a Privy server wallet and a spend policy owned by a separate 2-of-2 key quorum.
Sell the answer, keep the method: Chainlink CRE Confidential Workflows
What a confidential workflow is, how Chainlink runs one, how it lets a paid agent sell a verdict without publishing its edge, and where it stops.
TVL is not depth: what a Uniswap pool can actually trade
Why a pool's total value locked says little about whether it can take a trade or pay its LPs, and how a paid analyst measures depth, compares it with TVL and says how sure it is.