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Base Swap — Conditional (Validity Transaction)
x402
Base Swap — Conditional (Validity Transaction) is a paid API for AI agents from 402.com.tr, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-17).
Returns a signed, dormant 0x swap transaction on Base that is only included by the sequencer when user-defined conditions (block range, ETH balance, storage/price predicate) are met.
Price / call$0.02
Success—
StatusUnknown
How this service works
The base-swap 0x trade as a Cobalt validity transaction: Base includes your signed tx only while your conditions hold — a conditional order with no limit-order contract and nobody holding the trade. We never hold funds or keys; you sign and submit. Every request carries the deadline Base requires (at most 60 s out; set for you if omitted). Optional conditions: fromBlock, flashblockIndex (1-10), minNativeBalanceWei, or a caller-supplied storage predicate for price.
Output
A signed validity transaction payload wrapping the 0x-routed swap. The transaction is inert until the Base sequencer evaluates the attached conditions (beforeBlock, fromBlock, flashblockIndex, minNativeBalanceWei, or storage predicate). When conditions are satisfied the transaction is included; if they are never met it simply expires. No funds or keys are custodied by the service.
Example use cases
Good-till-block token swap
“I want to swap 1000 USDC for WETH on Base from my wallet 0xABC… but only if it gets included before block 13000000 — can you set that up with 100 bps slippage so the trade cancels itself if the deadline passes?”
ETH-balance-gated DCA purchase
“Buy 200 USDC worth of cbETH on Base from 0xDEF… but only execute the swap if my wallet still has at least 0.05 ETH in it — I don't want the swap to drain my gas reserve.”
On-chain price predicate swap
“Set up a conditional swap on Base: sell 500 DAI for ETH from wallet 0x123…, but only trigger it when the Uniswap V3 USDC/ETH pool storage slot 0x0 on contract 0x456… reads less than 0x186A0 — use 150 bps slippage and a deadline of block 14000000.”
Technical details
Endpoint
GEThttps://402.com.tr/api/x402/base-swap-validity?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a conditional or time-bounded swap on Base without deploying a limit-order contract and without custodying funds. It is ideal for good-till-block orders, balance-gated trades, flashblock-targeted execution, or on-chain price-predicate triggers. Prefer the plain Base Swap endpoint for immediate unconditional execution. Use this endpoint when you want the swap to self-cancel if conditions are never met, and when you want the taker to retain custody of keys throughout.
Side effects
- Missing required condition — at least one of beforeBlock, fromBlock, flashblockIndex, minNativeBalanceWei, or storageSlot must be provided
- Invalid taker address format returns a 400 error
- 0x routing failure if no liquidity path exists for the sell/buy pair on Base
- beforeBlock already passed at request time — transaction would be immediately invalid
- storageOp provided without storageSlot/storageAddress/storageValue — incomplete predicate rejected
- Slippage too tight causing 0x quote failure
- Amount of zero or negative rejected
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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