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The create-tx endpoint is intended to be used for both estimating and constructing order transactions. There are detailed breakdowns of parameters and the response fields. We do recommend reading deeper into these articles, but if you want to get up and running, have a look at the quick start section. Swagger specs of create-tx can be found here.

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Paired Quote and Transaction

The create-tx ednpoint is intentionally dual-purpose:
  • It estimates a realistic, market-aware outcome (estimation)
  • It constructs a ready-to-sign transaction (tx) whenever the call includes the necessary wallet data
This design intentionally removes the distinction between “get quote” and “build transaction” that exists in typical single-chain swap APIs. A detailed parameter reference & field-by-field response breakdown lives in the API Parameters and API Response sub-pages, while Swagger specs for create-tx can be explored here. For a hands-on walk-through, see the Quick Start section of the docs.

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Why Quote and Transaction Are Paired

DLN works with intent-based orders that traverse two independent blockchains, two swaps, and several off-chain actors (API, solvers, validators). An accurate quote must already account for:
  • Source-chain liquidity and gas
  • Destination-chain liquidity and gas
  • A solver’s operating expenses and target margin
  • Short-term market volatility during the time the order is in flight
  • Generating that quote is the most computationally expensive step; producing the transaction payload afterwards is trivial. A “lightweight quote” would be misleading and would cause orders to be ignored by solvers.

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How the create-tx Endpoint Behaves

ScenarioReturned FieldsTypical Use-Case
All required fields present (wallet connected, amounts known)estimation and txProduction trade flow
Wallet address missing (connect-wallet screen, fiat on-ramp flow)estimationPre-trade previews, fiat on-ramp flows
If dstChainTokenOutRecipient, srcChainOrderAuthorityAddress, or dstChainOrderAuthorityAddress are absent, the API withholds tx. Recipient and authorities parameters are required for creating the transaction. Replay the same call once addresses are known to receive the full response pair.

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Do Not Replay the Quote Into a Second Call

Passing the returned srcChainTokenInAmount and dstChainTokenOutAmount back to create-tx forces the endpoint into limit-order quoting strategy (both amounts fixed). Limit orders can drive solver profit negative, so they are typically ignored—use the original quote + transaction pair and let the user sign immediately.
Replay-and-fixing the amounts:
  • Converts a healthy market order into a potentially unattractive limit order
  • Slashes the fulfillment probability
Placing limit orders is fine but they can end up being unprofitable and remain unfilled. If more than ~30 seconds have passed, request a fresh quote-plus-transaction pair instead of re-using stale numbers. Profitable market orders are filled within seconds; unprofitable ones linger until they become profitable or the user cancels them.

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Timing Guarantees

Quotes remain solvent if the paired transaction is signed and broadcast within ~30 seconds. Beyond that window:
  • Gas cost or price movements may exceed the solver’s margin.
  • Solvers will skip the order; users must cancel and retry.
For ERC-20 flows with prependOperatingExpenses=true, approve a slightly higher allowance (≈ +30 %) or approve infinity to avoid a second approval if operating expenses drift upward while the user is signing. 
// 1. Preview (wallet not yet connected)
const preview = await fetch(
  '/dln/order/create-tx?srcChainId=56&srcChainTokenIn=<token_in_address>&srcChainTokenInAmount=1000000&' +
  'dstChainId=43114&dstChainTokenOut=<token_out_address>&dstChainTokenOutAmount=auto'
).then(data => data.json());

// preview.estimation is present; preview.tx is undefined.

// 2. User connects wallet; replay with authority/recipient addresses
const full = await fetch(
  '/dln/order/create-tx?srcChainId=56&srcChainTokenIn=<token_in_address>&srcChainTokenInAmount=1000000&' +
  'dstChainId=43114&dstChainTokenOut=<token_out_address>&dstChainTokenOutAmount=auto&' +
  'dstChainTokenOutRecipient=<user_address>&srcChainOrderAuthorityAddress=<user_address>&' +
  'dstChainOrderAuthorityAddress=<user_address>'
).then(data => data.json());

// full.estimation and full.tx are now present.
// Sign full.tx within 30 s for >99.9 % fill probability.

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Key Takeaways

  • One endpoint, one response—never separate quote retrieval from transaction generation.
  • The estimate/transaction pair maximizes fulfillment probability by eliminating UI-induced latency.
  • When wallet addresses are unknown, call create-tx for estimation only, then repeat once addresses are set.
  • Re-using quoted amounts in a second request reduces the likelihood of order fulfillment and should be avoided.
Following this pattern ensures that orders hit the network with fresh spreads, remain attractive to solvers, and settle cross-chain in seconds.