Simulate call with Parity trace output

POSThttps://api.triport.io/v1/polygon/trace/call

Executes a contract call against the state of a chosen Polygon block and returns the full Parity-style execution trace — without broadcasting anything.

Polygon—pro tier and above — RPS per tier with a ×2 burst allowance

POST /v1/polygon/trace/call simulates an eth_call against a chosen Polygon block and returns a structured Parity-style trace of the execution instead of just the call's return data. Nothing is broadcast and no state is persisted — the call is evaluated read-only against the state at the block you name. Use it to debug why a call reverts, to inspect the internal call tree and gas accounting, or to preview a transaction's effect before sending it via POST /v1/polygon/sender/raw.

The shape of the trace is controlled by the tracers array. Each entry selects one output section: trace (the call/create tree), vmTrace (a VM-level step-by-step trace), and stateDiff (the set of state changes the call would produce). You may request any combination; sections you do not ask for are returned as null.

Exclusive availability. Parity trace_* methods are served on Polygon through a throughput-constrained, exclusively-available canal. Because tracing is far more expensive than a plain read, this endpoint is gated to the pro tier and above, and is rate-limited more tightly than standard wallet reads — keep request rates modest and batch trace work where you can.

Parameters

This endpoint takes a JSON request body. All three top-level fields are required.

txobjectrequired

The transaction-call object to simulate. All EVM call fields are optional individually — see below.

tracersarray of stringrequired

Which trace sections to produce. One or more of trace, vmTrace, stateDiff.

blockstringrequired

Block to evaluate the call against — a block number (hex or decimal) or a tag: latest, pending, safe, finalized.

tx fieldsobject

fromstringoptional

Sender address the call executes as (0x-prefixed). Defaults to the zero address.

tostringoptional

Target contract address. Omit to simulate a contract creation.

datastringoptional

Hex-encoded ABI call data (method selector + arguments).

valuestringoptional

Hex-encoded wei value to send with the call.

gasstringoptional

Hex-encoded gas limit for the call.

tracers valuesobject

Response

A Parity-style trace envelope. Sections you did not request in tracers are returned as null. The example below requested only trace:

outputstring

Hex-encoded return data of the top-level call.

tracearray

Flat list of call/create frames. Present when trace was requested, otherwise null.

trace[].actionobject

Frame inputs: callType, from, to, value, gas, input.

trace[].resultobject

Frame outputs: gasUsed, output. Replaced by an error field if the frame reverted.

trace[].subtracesinteger

Number of direct child frames.

trace[].traceAddressarray

Position of this frame within the call tree.

trace[].typestring

Frame type: call, create, suicide, etc.

vmTraceobject

VM-level step trace. Present when vmTrace was requested, otherwise null.

stateDiffobject

Per-account state changes. Present when stateDiff was requested, otherwise null.

Errors

Code	Meaning	When it happens
400	`invalid_params`	Missing `tx`, `tracers`, or `block`; an unknown tracer name; or a malformed call object / block tag.
401	`unauthorized` / `trial_expired` / `subscription_expired`	No or invalid credentials, or the key's trial / subscription has ended.
403	`tier_insufficient` / `method_unknown`	Key is below the pro tier, or trace is not part of the key's product.
429	`rate_limited`	Sustained RPS for your tier exceeded; honour the `Retry-After` header and back off.

See errors.md for the full error envelope, the per-code body shapes, and the X-RateLimit-* headers returned on 429.

Examples

JavaScript (fetch)

JavaScript

const res = await fetch("https://api.triport.io/v1/polygon/trace/call", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.TRIPORT_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    tx: {
      from: "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
      to: "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
      data: "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064",
    },
    tracers: ["trace"],
    block: "latest",
  }),
});
const envelope = await res.json();
console.log(envelope.trace);

TypeScript SDK (`@triport/sdk`)

TypeScript

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


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


const envelope = await triport.polygon.trace.call({
  tx: {
    from: "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
    to: "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
    data: "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064",
  },
  tracers: ["trace"],
  block: "latest",
});
console.log(envelope.trace);

Python (`triport-sdk`)

Python

import os
from triport import Triport


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


envelope = triport.polygon.trace.call(
    tx={
        "from": "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
        "to": "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
        "data": "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064",
    },
    tracers=["trace"],
    block="latest",
)
print(envelope["trace"])

Notes

A call that reverts is still a successful (200) response: the revert surfaces inside the trace as an error field on the offending frame, not as a top-level HTTP error.
Request only the tracers sections you need. vmTrace in particular can produce very large bodies for complex calls.
To trace a transaction that has already been mined rather than a simulated call, use POST /v1/polygon/trace/replay-tx.
Authentication also accepts the X-API-Key header or the legacy ?api-key= query parameter — see authentication.md. Bearer is recommended.
For tier thresholds and how RPS-with-burst limiting works, see rate-limits-and-tiers.md.

Request

cURLJavaScriptPython

curl https://api.triport.io/v1/polygon/trace/call \
  -H "Authorization: Bearer $TRIPORT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "tx": {
      "from": "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
      "to": "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
      "data": "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064"
    },
    "tracers": ["trace"],
    "block": "latest"
  }'

const res = await fetch("https://api.triport.io/v1/polygon/trace/call", {
  method: "POST",
  headers: {
    "Authorization": "Bearer $TRIPORT_API_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "tx": {
      "from": "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
      "to": "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
      "data": "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064"
    },
    "tracers": [
      "trace"
    ],
    "block": "latest"
  }),
});
const data = await res.json();
console.log(data);

import requests


resp = requests.post(
    "https://api.triport.io/v1/polygon/trace/call",
    headers={
        "Authorization": "Bearer $TRIPORT_API_KEY",
        "Content-Type": "application/json",
    },
    json={
        "tx": {
            "from": "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
            "to": "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
            "data": "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064",
        },
        "tracers": [
            "trace",
        ],
        "block": "latest",
    },
)
data = resp.json()
print(data)

Response 200

JSON

{
  "output": "0x0000000000000000000000000000000000000000000000000000000000000001",
  "stateDiff": null,
  "trace": [
    {
      "action": {
        "callType": "call",
        "from": "0x8894e0a0c962cb723c1976a4421c95949be2d4e3",
        "to": "0x2791bca1f2de4661ed88a30c99a7a9449aa84174",
        "value": "0x0",
        "gas": "0x13880",
        "input": "0xa9059cbb0000000000000000000000005b38da6a701c568545dcfcb03fcb875f56beddc40000000000000000000000000000000000000000000000000000000000000064"
      },
      "result": {
        "gasUsed": "0x6c1c",
        "output": "0x0000000000000000000000000000000000000000000000000000000000000001"
      },
      "subtraces": 0,
      "traceAddress": [],
      "type": "call"
    }
  ],
  "vmTrace": null
}