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Build transactions

post

https://api.mevx.io/swap/api/v1/transaction/build

Build exact-input swap transactions without broadcasting them.

Recommended unsigned flow

Omit wallets.privateKey. The response contains unsignedTransactions; sign every entry locally, then submit the signed values through /swap/api/v1/transaction with type: "submit".

If wallets.privateKey is supplied, the response contains signed transactions in result. Avoid this mode unless your backend can handle private keys securely.

Supported routes

Chain	Exchanges/routes
Solana	Pump.fun, PumpAMM, Raydium CLMM/CPMM, Jupiter
Ethereum	Uniswap V2/V3
Base	Uniswap V2/V3
BSC	Fourmeme, PancakeSwap V2

Only exact-input swaps are supported. Route availability can vary by deployment configuration.

Jupiter

Jupiter supports Solana only, returns exactly one unsigned transaction, does not support tax or buildAndSubmit, and ignores MEV settings. Sign the returned transaction without modifying its message. When submitting, return the unchanged requestId and lastValidBlockHeight; the order is bound to the API credential and cannot be replayed after successful execution.

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Body Params

Create the plaintext JSON described below, then encrypt it. The private key is optional and should normally be omitted.

The HTTP body is encrypted text. Before encryption, create this JSON object:

Decrypted JSON field	Required	Description
`chain`	Yes	`sol`, `eth`, `bsc`, or `base`
`exchange`	Yes	`pump`, `pump.fun`, `pumpamm`, `raydium`, `jupiter`, `uniswap`, `fourmeme`, or `pancakeswap`; see compatibility table below
`type`	Yes	`exactIn`; exact-output builds are not supported
`side`	Yes	`buy` or `sell`
`swap.exactInAmount`	Yes	Human-readable input-token amount, supplied as a string
`swap.slippage`	No	Maximum slippage percentage, supplied as a string
`swap.minOutAmount`	No	Minimum human-readable output-token amount
`swap.exactOutAmount`	Reserved	Exact-output is unsupported; omit or set numeric zero
`swap.maxInAmount`	Reserved	Exact-output is unsupported; omit or set numeric zero
`wallets.address`	Yes	Wallet public address
`wallets.id`	No	Your wallet identifier
`wallets.privateKey`	No	Omit to receive `unsignedTransactions`; include only for server-side signing
`poolAddress`	Route-specific	Required for direct pool routes; omit for Jupiter
`baseToken`	Route-specific	Base token address or mint
`quoteToken`	Route-specific	Quote token address or mint; required for a requested Jupiter pair
`sltp`	No	Up to 10 stop-loss/take-profit entries with `curvePercent`, `duration`, `percentInAmount`, `profitPercent`, and `slippage`
`setting`	No	Supports `antiMev`, `antiMevProvider`, `mevPriorityFee`, `mevTip`, `priorityFee`, and `wrappedNative`
`tax.receiverAddress`	Tax only	Fee recipient address
`tax.type`	Tax only	Only `percent` is supported
`tax.value`	Tax only	Percentage string from `0.01` through `10`

Exchange options

Chain	Values
Solana	`pump` (or alias `pump.fun`), `pumpamm`, `raydium`, `jupiter`
Ethereum	`uniswap`
Base	`uniswap`
BSC	`fourmeme`, `pancakeswap`

setting options

Field	Type/default	Description
`antiMev`	boolean, `false`	Enable protected submission
`antiMevProvider`	enum, optional	Choose from the provider table below; omit to use the configured chain default
`mevPriorityFee`	numeric string	Provider priority fee in the chain native token
`mevTip`	numeric string	Provider tip in the chain native token
`priorityFee`	numeric string	Standard priority fee in the chain native token
`wrappedNative`	boolean, `false`	Request wrapped-native-token behavior where supported

antiMevProvider options

Set setting.antiMev to true, then optionally select one of these exact values:

Chain	`antiMevProvider` values
Solana	`jito`, `nextblock`, `temporal`, `cbase`, `zeroslot`, `bloxroute`
BSC	`bloxroute`
Ethereum	Not supported
Base	Not supported

Jupiter ignores anti-MEV settings because it handles landing.

Recommended plaintext example:

{
  "chain": "sol",
  "exchange": "raydium",
  "poolAddress": "POOL_ADDRESS",
  "baseToken": "TOKEN_MINT",
  "type": "exactIn",
  "side": "buy",
  "swap": {
    "exactInAmount": "1",
    "slippage": "1"
  },
  "wallets": {
    "address": "YOUR_WALLET_ADDRESS",
    "id": "wallet_1"
  },
  "setting": {
    "priorityFee": "0.0001"
  }
}

Stringify this object, encrypt it as AES-256-GCM using 12-byte nonce || ciphertext || 16-byte tag, encode it with unpadded Base64URL, and send that string as the text/plain body. The ReadMe Node.js sample performs these steps.

Responses

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Response

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application/json