alchemy_simulateAssetChanges

POSThttps://api.triport.io/v1/eth

Simulates a single transaction against the latest state and returns the asset balance changes (ETH, ERC-20, ERC-721, ERC-1155) it would produce — without broadcasting it.

Ethereum—Pro — 5 RPS · Business — 15 RPS (with burst)

alchemy_simulateAssetChanges runs a transaction through the EVM against the current chain state and reports the asset movements it would cause if it were mined now. Use it to preview the effect of a transaction — how much ETH and which tokens leave or enter each address — before asking a user to sign, so you can show an accurate "you will send / you will receive" summary and catch unexpected approvals or transfers.

The simulation is read-only: the transaction is not submitted to the network and no gas is spent. Results reflect the latest committed state at the time of the call, so a transaction that simulates cleanly can still revert or produce different changes once on-chain if state shifts in between.

This method belongs to the eth_trace category and is available on the Pro tier (5 RPS) and Business tier (15 RPS). A request from a lower tier returns -32002 (tier_insufficient).

Parameters

A single positional parameter: the transaction object to simulate. Fields use the same hex-quantity and hex-data encoding as eth_call / eth_sendTransaction.

transactionobjectrequired

The transaction to simulate.

transaction.fromstring (address)required

Sender address; balance changes are computed relative to this account.

transaction.tostring (address)optional

Recipient or contract address. Omit for contract-creation simulations.

transaction.valuestring (hex quantity)optional

Wei to send, hex-encoded (e.g. "0xde0b6b3a7640000" for 1 ETH). Defaults to 0x0.

transaction.datastring (hex data)optional

Call data / encoded function call.

transaction.gasstring (hex quantity)optional

Gas limit for the simulation.

Response

Response fields

Field	Type	Description
`jsonrpc`	string	JSON-RPC protocol version, always `"2.0"`.
`id`	number \| string	Echoes the request `id`.
`result`	object	The simulation outcome.
`result.changes`	array	One entry per asset movement the transaction would cause. Empty if it moves no assets.
`result.changes[].assetType`	string	Asset class: `NATIVE` (ETH), `ERC20`, `ERC721`, or `ERC1155`.
`result.changes[].changeType`	string	`TRANSFER` or `APPROVE`.
`result.changes[].from`	string (address)	Address the asset leaves.
`result.changes[].to`	string (address)	Address the asset arrives at.
`result.changes[].rawAmount`	string	Amount in base units (no decimal scaling).
`result.changes[].amount`	string	Human-readable amount, scaled by `decimals`.
`result.changes[].symbol`	string \| null	Token symbol, when known.
`result.changes[].decimals`	number \| null	Token decimals, when known.
`result.changes[].contractAddress`	string \| null	Token contract; `null` for native ETH.
`result.changes[].tokenId`	string \| null	Token id for ERC-721 / ERC-1155; `null` otherwise.
`result.gasUsed`	string (hex quantity)	Gas the transaction consumed in simulation.
`result.error`	string \| null	Revert reason if the transaction would revert; `null` on success.

Errors

Code	Meaning	When it happens
`-32002`	`tier_insufficient`	Your plan is below the Pro tier required for `alchemy_simulateAssetChanges`. The error `data` includes `current_tier`, `required_tier`, and an `upgrade_url`.
`-32003`	`rate_limited`	You exceeded your tier's RPS limit (5 RPS on Pro, 15 RPS on Business). The error `data` includes `limit_rps`, `burst_capacity`, and `retry_after_sec`.

Example error envelope (tier too low):

JSON

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32002,
    "message": "tier insufficient for method alchemy_simulateAssetChanges",
    "data": {
      "method": "alchemy_simulateAssetChanges",
      "category": "eth_trace",
      "chain": "eth",
      "current_tier": "free",
      "required_tier": "pro",
      "upgrade_url": "https://api.triport.io/upgrade"
    }
  }
}

Example error envelope (rate limited):

JSON

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32003,
    "message": "Rate limit exceeded: 5 RPS sustained on eth_trace (pro tier)",
    "data": {
      "current_tier": "pro",
      "category": "eth_trace",
      "limit_rps": 5,
      "burst_capacity": 10,
      "retry_after_sec": 1
    }
  }
}

A 429 also carries a Retry-After header. See errors.md for the full error envelope and the shared error-code reference.

Examples

JavaScript (fetch)

JavaScript

const res = await fetch("https://api.triport.io/v1/eth", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.TRIPORT_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    id: 1,
    method: "alchemy_simulateAssetChanges",
    params: [
      {
        from: "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
        to: "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
        value: "0xde0b6b3a7640000",
        data: "0x",
      },
    ],
  }),
});


const { result } = await res.json();
for (const change of result.changes) {
  console.log(`${change.amount} ${change.symbol}: ${change.from} -> ${change.to}`);
}

TypeScript SDK (`@triport/sdk`)

TypeScript

import { Triport } from "@triport/sdk";


const client = new Triport({ apiKey: process.env.TRIPORT_API_KEY });


const result = await client.eth.request("alchemy_simulateAssetChanges", [
  {
    from: "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
    to: "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
    value: "0xde0b6b3a7640000",
    data: "0x",
  },
]);


console.log(result.changes);

Python (`triport-sdk`)

Python

import os
from triport import Triport


client = Triport(api_key=os.environ["TRIPORT_API_KEY"])


result = client.eth.request("alchemy_simulateAssetChanges", [
    {
        "from": "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
        "to": "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
        "value": "0xde0b6b3a7640000",
        "data": "0x",
    },
])


for change in result["changes"]:
    print(change["amount"], change["symbol"], change["from"], "->", change["to"])

Notes

The transaction is simulated against the latest committed state and is never broadcast — re-simulate just before signing for time-sensitive flows, since state can move between the call and the on-chain inclusion.
If the transaction would revert, result.error carries the revert reason and result.changes reflects only the changes up to the revert point.
Requires the Pro tier or higher; a lower tier returns -32002 (tier_insufficient).
Rate limiting is RPS-per-tier with burst; there is no daily quota.
To simulate a sequence of transactions together rather than a single one, see alchemy_simulateExecutionBundle.

Request

cURLJavaScriptPython

curl https://api.triport.io/v1/eth \
  -H "Authorization: Bearer $TRIPORT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "alchemy_simulateAssetChanges",
    "params": [
      {
        "from": "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
        "to": "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
        "value": "0xde0b6b3a7640000",
        "data": "0x"
      }
    ]
  }'

const res = await fetch("https://api.triport.io/v1/eth", {
  method: "POST",
  headers: {
    "Authorization": "Bearer $TRIPORT_API_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "jsonrpc": "2.0",
    "id": 1,
    "method": "alchemy_simulateAssetChanges",
    "params": [
      {
        "from": "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
        "to": "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
        "value": "0xde0b6b3a7640000",
        "data": "0x"
      }
    ]
  }),
});
const data = await res.json();
console.log(data);

import requests


resp = requests.post(
    "https://api.triport.io/v1/eth",
    headers={
        "Authorization": "Bearer $TRIPORT_API_KEY",
        "Content-Type": "application/json",
    },
    json={
        "jsonrpc": "2.0",
        "id": 1,
        "method": "alchemy_simulateAssetChanges",
        "params": [
            {
                "from": "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
                "to": "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
                "value": "0xde0b6b3a7640000",
                "data": "0x",
            },
        ],
    },
)
data = resp.json()
print(data)

Response 200

JSON

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "changes": [
      {
        "assetType": "NATIVE",
        "changeType": "TRANSFER",
        "from": "0xf1a726210550c306a9964b251cbcd3fa5ecb275d",
        "to": "0x2e2ed0cfd3ad2f1d34481277b3204d807ca2f8c2",
        "rawAmount": "1000000000000000000",
        "amount": "1.0",
        "symbol": "ETH",
        "decimals": 18,
        "contractAddress": null,
        "tokenId": null
      }
    ],
    "gasUsed": "0x5208",
    "error": null
  }
}

alchemy_simulateAssetChanges

Parameters

Response

Response fields

Errors

Examples

JavaScript (fetch)

TypeScript SDK (@triport/sdk)

Python (triport-sdk)

Notes

TypeScript SDK (`@triport/sdk`)

Python (`triport-sdk`)