Turns a stored quote into unsigned transactions for the taker to sign and send. arcgate never signs, broadcasts or holds funds.

• Cost: 0.01 USDC under $1,000; 0.05 USDC from $1,000 to $10,000; above that 0.05 USDC plus 0.5 bps of the amount over $10,000, capped at 5 USDC, size-tiered by the quote's USD notional (the USDC side for a USDC pair, or a token-to-token quote's USD valuation; a quote with no valuation prices at tier 1), over x402 (402 with PAYMENT-REQUIRED, retry with PAYMENT-SIGNATURE). Charged once per quote: POST /trade/v1/swap/tx, the Permit2 second round below, is free.

• Key inputs: quoteId (from POST /trade/v1/quote), taker; optional recipient (defaults to taker), deadlineSec, approval. Never permit - that belongs to POST /trade/v1/swap/tx; sending one here is 400 invalid_request (the strict schema rejects the unknown key).

• Every quote executes through ArcgateRouter: it is always the Permit2 spender and the ERC-20 approve spender below. When every source pool of the route being executed trades native USDC, the swap is funded by value instead - no approval transaction and no signature at all.

• Permit2 (default, one or two calls):

  • Returns transactions - an unlimited ERC-20 approve(Permit2, type(uint256).max) first, if the token's ERC-20 allowance to Permit2 is below the amount, then the swap, which carries an empty Permit2 signature and is only directly sendable as-is when a Permit2 allowance to ArcgateRouter already covers the amount, in which case signatures is empty too. Otherwise it also returns signatures: [{ kind: "permit2", typedData }]; sign typedData with the taker's key (EIP-712, e.g. viem's signTypedData).

  • Sign, then call POST /trade/v1/swap/tx with the same quoteId, taker and recipient, and permit: { message: typedData.message, signature }, while the quote is live: free, because this call already paid the swap fee. The first call to it that succeeds uses the round up; a failed one doesn't.

  • Send that response's transactions in order.

• approval: "approve" (one call): returns at most one ERC-20 approve(ArcgateRouter, amountIn) transaction instead of a permit to sign - an exact amount, never Permit2, never a signature - and only when the taker's current allowance is below it.

• Freshness: the quote lives for the ttlSec the quote call asked for (default/max 120s); after that quoteId is 410 quote_expired. Every call re-quotes and re-simulates at the current block and returns 409 quote_stale when the fresh re-quote fails or falls below the stored minAmountOut, when the pre-flight simulation reverts on slippage, or when the simulated delivery is below minAmountOut. A 409 or 410 carries a free fresh quote in quote, with next: "requote": the original quote request (same amount, tokens, side, slippageBps and venues, default ttlSec) quoted again through the same pipeline, exactly as POST /trade/v1/quote answers it; when the original named a taker, the fresh quote is for this call's taker, the wallet swapping now. Nothing executes on it: check its price, safety.verdict and readiness, then swap its quoteId. When the fresh quote can't be traded (no_route, insufficient_liquidity, unsupported_venue or buy_reverts, a cannot_sell or illiquid verdict, not executable, or the taker isn't ready) the answer is next: "stop" with no quote, and error.hint says why. One fresh quote per paid quote: a second 409/410 for the same quoteId, a quote that itself came from a 409/410, or a quote expired over 5 minutes ago gets plain requote with no quote, as does one whose re-quote couldn't run or failed on the server's side; then quote again yourself.

• Fallback: A stored route on a disabled/undeployed venue falls back to the best executable candidate the quote already priced (warning route_not_executable), or 422 not_executable when no such candidate exists, none re-quotes, or no ArcgateRouter is configured at all.

• Attempts: a quote gets at most 5 failed calls here; the next call on that quoteId is 429 swap_attempts_exhausted (next: "requote"), answered without running the swap pipeline. A failed call is a 409, a 410 (its fresh quote may run), a 422, 500 or 503, or a successful pipeline whose payment settlement or delivery fails. An attempt stays reserved until its 200 is delivered (after settlement when paid); that delivery, a 404, or a 400 (at parse, or a reserved taker/recipient) uses none. A delivered 200 does not reset this quote's previous failures. POST /trade/v1/swap/tx counts its own, per permit round.

• Next: a 200 with signatures non-empty needs POST /trade/v1/swap/tx before sending anything (next: "sign_permit"); otherwise sign and send transactions in order, then confirm the fill with POST /trade/v1/receipt (free). Costs 0.01 USDC under $1,000; 0.05 USDC from $1,000 to $10,000; above that 0.05 USDC plus 0.5 bps of the amount over $10,000, capped at 5 USDC; the exact amount for your quoteId comes back in the payment-required result. Payment goes in params._meta["x402/payment"]; use an x402-aware MCP client (see https://docs.arcgate.dev/#arcgate/description/mcp-for-agents).