Validating Transactions

The validate endpoint ensures that the unsigned transaction you’re about to sign matches exactly what was simulated. Each field is checked independently, so you know precisely what changed if validation fails.

POST https://quoter.api.enso.build/api/v1/validate

Request Parameters

Field	Type	Required	Description
`simulationId`	`string` (UUID)	Yes	The `simulationId` from a prior `/simulate` call
`transaction.data`	`string`	Yes	Hex-encoded calldata
`transaction.to`	`string`	Yes	Target contract address
`transaction.from`	`string`	Yes	Sender address
`transaction.value`	`string`	Yes	Native token value in wei
`transaction.chainId`	`number`	Yes	Chain ID

Response

Field	Type	Description
`valid`	`boolean`	`true` only when all checks pass
`simulationId`	`string`	The simulation ID validated against
`checks.chainId`	`boolean`	Chain ID matches
`checks.data`	`boolean`	Calldata hash matches
`checks.to`	`boolean`	Target contract address matches
`checks.from`	`boolean`	Sender address matches
`checks.value`	`boolean`	Native token value matches

Examples

Successful Validation

curl -X POST https://quoter.api.enso.build/api/v1/validate \
  -H "Authorization: Bearer $ENSO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "simulationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "transaction": {
      "data": "0x3593564c...",
      "to": "0x80EbA3855878739F4710233A8a19d89Bdd2ffB8E",
      "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      "value": "1000000000000000000",
      "chainId": 1
    }
  }'

const result = await fetch("https://quoter.api.enso.build/api/v1/validate", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${ENSO_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    simulationId: "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    transaction: {
      data: "0x3593564c...",
      to: "0x80EbA3855878739F4710233A8a19d89Bdd2ffB8E",
      from: "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      value: "1000000000000000000",
      chainId: 1,
    },
  }),
}).then((res) => res.json());

Response:

{
  "valid": true,
  "simulationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "checks": {
    "chainId": true,
    "data": true,
    "to": true,
    "value": true,
    "from": true
  }
}

Failed Validation (Tampered Data)

If the calldata has been modified since simulation, the data check will fail:

{
  "valid": false,
  "simulationId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "checks": {
    "chainId": true,
    "data": false,
    "to": true,
    "value": true,
    "from": true
  }
}

Interpreting Failed Checks

Check	When `false`	Likely Cause
`data`	Calldata was modified	Transaction payload was tampered with, or a different function/arguments were encoded
`to`	Target contract changed	The transaction is being sent to a different contract than simulated
`from`	Sender changed	A different account is submitting the transaction
`value`	ETH value changed	The native token amount was modified
`chainId`	Wrong chain	The transaction is targeting a different chain than simulated

If any check fails, do not sign the transaction. Re-simulate to get a fresh simulationId, or investigate why the transaction changed.

Cache Expiry

Simulations are cached for 5 minutes. If you call /validate after the simulation has expired, you’ll receive a 404 error:

{
  "statusCode": 404,
  "message": "Simulation a1b2c3d4-e5f6-7890-abcd-ef1234567890 not found or expired"
}

Re-simulate to get a fresh simulationId and try again.

Best Practices

Validate immediately before signing — Don’t validate far in advance. Validate as close to the signing moment as possible within the 5-minute window.
Log the simulationId — Store simulation IDs for debugging and audit trails.
Re-simulate on failure — If validation fails, re-simulate to get a fresh result rather than retrying the same validation.
Check individual fields — When valid is false, inspect the checks object to understand exactly what changed.

async function safeSign(simulationId: string, tx: UnsignedTransaction) {
  const validation = await validate(simulationId, tx);

  if (!validation.valid) {
    const failedChecks = Object.entries(validation.checks)
      .filter(([, passed]) => !passed)
      .map(([field]) => field);

    throw new Error(`Validation failed for: ${failedChecks.join(", ")}`);
  }

  return await wallet.sendTransaction(tx);
}

Updated

Quoter

Guides

Reference

API Reference

Request Parameters

Response

Examples

Successful Validation

Failed Validation (Tampered Data)

Interpreting Failed Checks

Cache Expiry

Best Practices

​Request Parameters

​Response

​Examples

​Successful Validation

​Failed Validation (Tampered Data)

​Interpreting Failed Checks

​Cache Expiry

​Best Practices

Request Parameters

Response

Examples

Successful Validation

Failed Validation (Tampered Data)

Interpreting Failed Checks

Cache Expiry

Best Practices