trace_call

trace_call executes a single call against the chain state at a given block (no broadcast, no state mutation) and returns the complete Parity trace array for that call. Optionally it also returns a state diff and/or a low-level VM trace, depending on the trace types you request.

It is the lightweight sibling of trace_block: instead of re-executing every transaction in a block, it runs exactly one call, so it is fast enough for interactive and pre-confirmation use. The primary use case is MEV pre-confirmation analysis — simulate a candidate transaction (or a single leg of a sandwich bundle) and read the full internal call tree to compute expected profit before you sign and broadcast. A plain eth_call only returns the final return data; trace_call exposes every internal call, value transfer, and (optionally) storage change along the way.

This is a premium capability: it requires the polygon_trace scope and Pro tier or higher. Calls below Pro tier are rejected with -32002, and calls that exceed your tier's per-second rate are rejected with -32003.

Positional params array: [transaction, traceTypes, blockTag].

Response fields

The result object:

Each entry in trace describes one internal call frame:

See the shared errors reference for the full error envelope and the structure of the data field.

JavaScript (fetch)

const res = await fetch("https://api.triport.io/v1/polygon", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.TRIPORT_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    id: 1,
    method: "trace_call",
    params: [
      {
        from: "0xa1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
        to: "0x7ceb23fd6bc0add59e62ac25578270cff1b9f619",
        value: "0x0",
        data: "0x70a08231000000000000000000000000a1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
      },
      ["trace"],
      "latest",
    ],
  }),
});


const { result } = await res.json();
console.log(result.trace);

TypeScript SDK (@triport/sdk)

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


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


const result = await client.polygon.rpc("trace_call", [
  {
    from: "0xa1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
    to: "0x7ceb23fd6bc0add59e62ac25578270cff1b9f619",
    value: "0x0",
    data: "0x70a08231000000000000000000000000a1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
  },
  ["trace"],
  "latest",
]);


console.log(result.output, result.trace);

Python (triport-sdk)

import os
from triport import Triport


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


result = client.polygon.rpc(
    "trace_call",
    [
        {
            "from": "0xa1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
            "to": "0x7ceb23fd6bc0add59e62ac25578270cff1b9f619",
            "value": "0x0",
            "data": "0x70a08231000000000000000000000000a1b2c3d4e5f60718293a4b5c6d7e8f9001122334",
        },
        ["trace"],
        "latest",
    ],
)


print(result["output"], result["trace"])

• Trace types control payload size. Request only what you need. ["trace"] returns the call tree and is the lightest option. Adding "stateDiff" returns every touched storage slot, and "vmTrace" returns a per-opcode execution log — both can grow the response substantially.
• Pre-confirmation MEV workflow. Simulate a candidate transaction against latest (or pending) state, walk the returned trace to follow internal token flows and value transfers, and compute expected profit before signing. Because nothing is broadcast, you can probe many candidate inputs cheaply.
• Parity shape, not Geth. This method returns the Parity trace format (action / result / subtraces / traceAddress). It is a different shape from Geth-style debug tracing — if your tooling consumes the Geth calls tree, you will need an adapter.
• Block tags. Use latest for real-time pre-confirmation analysis and a hex block number for reproducible historical simulation. pending reflects the current pending state.
• Related methods: trace_block (full block call tree), trace_transaction (trace one already-mined tx), trace_filter (range/address filter over historical traces), and trace_replayBlockTransactions (full block replay with state diff). For an unsimulated read of final state only, use eth_call.