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The Market API splits a swap into price discovery (off-chain) and execution (on-chain). You ask for a route, you build calldata against that route, and your user signs and broadcasts the transaction. Settlement is atomic: the swap either completes in one transaction or reverts.

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The flow at a glance

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The four stages

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1. Price

You call GET /prices with srcToken, destToken, amount, side (SELL or BUY), and network. The aggregator scans liquidity across every major DEX it supports on that chain, evaluates multi-hop and multi-DEX paths, and returns a priceRoute containing the best path, the expected destAmount, the gas estimate, and a USD breakdown (srcUSD, destUSD, gasCostUSD). The priceRoute is stateless and unsigned: it’s just a routing plan. It expires quickly (prices move) but holds no commitment.

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2. Build

You POST /transactions/:chainId with the full priceRoute from step 1, the user’s address, and a slippage tolerance. The API returns ready-to-broadcast calldata: to (the Augustus v6.2 router on that chain), data (encoded swap call), value (native token to send, if any), and a gas estimate.
Pass the priceRoute verbatim. Mutating any field will cause the build call to reject.

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3. Approve (ERC-20 only)

If the source token is an ERC-20, the user must approve the Augustus v6.2 router as a spender before the swap. This is a standard approve(spender, amount) call. Native source tokens (ETH, MATIC, etc.) skip this step; value is sent with the swap tx directly. You can avoid this round-trip by passing permit or permit2 data in the build call.

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4. Settle

The user signs the swap transaction and broadcasts it. The Augustus router pulls srcToken, walks the path returned by the aggregator (each hop calls into the underlying DEX), checks the final destAmount against the user’s minDestAmount (price × 1 − slippage), and delivers destToken to the user. If any hop fails or slippage is exceeded, the entire transaction reverts; there’s no partial-fill state.

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Why this design

Atomic execution

The swap completes in one transaction or reverts. No half-filled state to clean up.

Composable

Augustus calldata can be wrapped in any contract call: vaults, batches, multicalls.

Best-price routing

Multi-hop, multi-DEX paths across every venue the aggregator supports on each chain.

Full user control

The user signs and broadcasts. No off-chain solver custody, no auction delay.
Last modified on June 14, 2026