Call a Chain Method

Use this endpoint to simulate a smart contract method call without changing on-chain state. Ideal for reading balances, metadata, or any other view/pure functions. No gas is consumed, and no wallet is required.

Prerequisites

Before you begin, ensure:

• You’ve correctly encoded your method calldata (txData)
• You know the target chainId

Endpoint

POST /v2/chain/call

Request Parameters

{
  "txData": "0xabcdef...",
  "chainId": 137,
  "sentAt": "2025-05-08T12:00:00Z"
}

• txData: Encoded calldata for the read-only method (e.g. balanceOf(address))
• chainId: Numeric ID of the chain to query (e.g. 137 for Polygon)
• sentAt: ISO timestamp for submission

Example Request

cURL

call-chain-method.sh

curl -X POST https://api.fsco.io/v2/chain/call \
  -H "Authorization: Bearer $FSCO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "txData": "0xabcdef...",
    "chainId": 137,
    "sentAt": "2025-05-08T12:00:00Z"
  }'

TypeScript

call-chain-method.ts

import axios from 'axios';

const FSCO_API_KEY = process.env.FSCO_API_KEY;

const callChainMethod = async () => {
  const response = await axios.post(
    'https://api.fsco.io/v2/chain/call',
    {
      txData: '0xabcdef...',
      chainId: 137,
      sentAt: '2025-05-08T12:00:00Z'
    },
    {
      headers: {
        Authorization: `Bearer ${FSCO_API_KEY}`,
        'Content-Type': 'application/json'
      }
    }
  );

  console.log('Chain method called:', response.data);
};

callChainMethod();

Python

call-chain-method.py

import requests
import os

FSCO_API_KEY = os.getenv("FSCO_API_KEY")

headers = {
    "Authorization": f"Bearer {FSCO_API_KEY}",
    "Content-Type": "application/json",
}

payload = {"txData": "0xabcdef...", "chainId": 137, "sentAt": "2025-05-08T12:00:00Z"}

response = requests.post(
    "https://api.fsco.io/v2/chain/call", json=payload, headers=headers
)

print("Chain method called:", response.json())

.NET

call-chain-method.cs

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        var apiKey = Environment.GetEnvironmentVariable("FSCO_API_KEY");

        var client = new HttpClient();
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);

        var json = @"{
            ""txData"": ""0xabcdef..."",
            ""chainId"": 137,
            ""sentAt"": ""2025-05-08T12:00:00Z""
        }";
        var content = new StringContent(json, Encoding.UTF8, "application/json");

        var response = await client.PostAsync("https://api.fsco.io/v2/chain/call", content);
        var responseString = await response.Content.ReadAsStringAsync();

        Console.WriteLine("Chain method called: " + responseString);
    }
}

Response

JSON

response.json

{
  "executionId": "12345678-1234-1234-1234-123456789012",
  "data": "0x00000000000000000000000000000000000000000000000000000000000003e8"
}

The response includes:

• executionId: An internal reference for the simulated call
• data: The raw return value of the method in hex format

Next Steps

• Execute a Transaction to change on-chain state
• Get Transaction by ID to check transaction status using the FSCO queryId
• Get Transaction by Hash to look up transaction details using the on-chain hash
• Learn more in the Chain module overview
• View the complete Chain API reference