# Ethereum eth_call Simulator (skills.onesource.io)

> Ethereum eth_call Simulator (skills.onesource.io) is a paid API for AI agents from skills.onesource.io, paid per call via x402, $0.005000/call, status unknown (last checked 2026-09-14).

Simulates a read-only Ethereum smart contract call via eth_call without sending a transaction to the chain

## Facts

- Endpoint: POST https://skills.onesource.io/api/chain/call
- Price: $0.005000/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/skills-onesource-io-4a1c9f57
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_I72duu9xA4PER4x-cAAjf

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability skills-onesource-io-4a1c9f57 -d '<json body>'
```

Example prompt: Simulate a read-only eth_call to Ethereum contract 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 with calldata 0x70a08231000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA96045 — no transaction, just return the result bytes.

## When to prefer this

Use this endpoint when you need to read on-chain Ethereum contract state or simulate a function call without sending a real transaction. Ideal for querying view/pure functions, checking balances, resolving on-chain mappings, or validating calldata before broadcasting. Prefer over alternatives when you need a raw eth_call with full control over to, data, from, and value fields rather than a higher-level abstraction.

## Known failure modes

- Invalid contract address format returns 400 validation error
- Malformed calldata hex string returns 400 validation error
- Contract reverts during simulation — returns revert reason or empty data
- Contract does not exist at the given address — returns 0x or error
- RPC node unavailable or rate-limited — returns 5xx error
- Insufficient USDC balance for x402 payment — payment gateway rejection

## How this service works

Simulate a read-only Ethereum contract call via eth_call - no transaction sent

## Output

Returns ABI-encoded bytes representing the return value of the simulated contract call, as if the function were executed on-chain at the current block without broadcasting a transaction or consuming real gas.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string",
   "pattern": "^0x[a-fA-F0-9]{40}$"
  },
  "data": {
   "type": "string",
   "pattern": "^0x[a-fA-F0-9]+$"
  },
  "from": {
   "type": "string",
   "pattern": "^0x[a-fA-F0-9]{40}$"
  },
  "value": {
   "type": "string",
   "pattern": "^0x[a-fA-F0-9]+$"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/skills-onesource-io-4a1c9f57/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from skills.onesource.io](https://www.zero.xyz/host/skills.onesource.io/llms.txt)