# Simulate Execution

> Simulate Execution is a paid API for AI agents from stablecrypto.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Simulates an Ethereum transaction and returns detailed execution traces without broadcasting to the network

## Facts

- Endpoint: POST https://stablecrypto.dev/api/alchemy/simulation/simulate-execution
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/simulate-execution-1428b447
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3Y7-Lo348eA24j-5lss8P

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 simulate-execution-1428b447 -d '<json body>'
```

Example prompt: Simulate this transaction on eth-mainnet for me before I send it — from 0xAbC...123 to the Uniswap v3 router at 0xE592...def with calldata 0xa9059cbb... and a value of 0x0, and show me the execution traces.

## When to prefer this

Use this endpoint when you need to preview or validate an Ethereum transaction's behavior before broadcasting — especially useful for smart contract interactions where you want to confirm the calldata is correct, anticipate revert reasons, or inspect the full execution trace. Prefer this over generic RPC passthrough when you need structured simulation output from Alchemy's trace engine rather than a raw eth_call.

## Known failure modes

- Invalid sender or recipient address returns a validation error
- Malformed calldata causes simulation revert with revert reason if available
- Unsupported network slug returns a network-not-found error
- Missing required fields (network, from, to) returns a 400 bad request
- Contract not deployed at target address on specified network causes simulation failure
- Rate limiting or upstream Alchemy API error returns a 5xx response

## How this service works

Pay-per-request access to CoinGecko, DefiLlama, Alchemy, and Etherscan APIs. No auth, no subscriptions.

## Output

Returns an object containing execution traces and simulation results for the given transaction, including call stack details, state changes, return values, and whether the transaction would succeed or revert — without actually submitting it to the network.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string",
   "description": "Contract/recipient address"
  },
  "data": {
   "type": "string",
   "description": "Transaction calldata"
  },
  "from": {
   "type": "string",
   "description": "Sender address"
  },
  "value": {
   "type": "string",
   "description": "ETH value in hex"
  },
  "network": {
   "type": "string",
   "description": "Alchemy network slug, e.g. eth-mainnet, base-mainnet"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/simulate-execution-1428b447/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stablecrypto.dev](https://www.zero.xyz/host/stablecrypto.dev/llms.txt)