# NodeFlare Transaction Simulation API

> NodeFlare Transaction Simulation API is a paid API for AI agents from rpc.nodeflare.app, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-13).

Simulates an EVM transaction before sending to determine if it will revert, estimate gas, and identify token/ETH balance changes.

## Facts

- Endpoint: POST https://rpc.nodeflare.app/data/simulate/x402?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/nodeflare-transaction-simulation-api-b423cdbc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_y7TA0tMiqQXQrxzK83GYr

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 nodeflare-transaction-simulation-api-b423cdbc -d '<json body>'
```

Example prompt: Before I submit this swap transaction on Ethereum — from 0xabc...123 calling 0xDef...456 with this calldata — can you simulate it to tell me if it'll revert, how much gas it'll use, and which tokens will move?

## When to prefer this

Choose this endpoint when you need to pre-validate an EVM transaction before signing and broadcasting — especially in agentic workflows where sending a failing transaction would waste gas or cause irreversible state changes. Ideal when you need both the revert prediction AND token flow analysis in a single call, rather than running a separate eth_call plus token event trace. Particularly useful for DeFi interactions, contract debugging, and any agent that must confirm transaction safety before user approval.

## Known failure modes

- Invalid or malformed transaction object returns a 400 error
- Unsupported chain ID returns an error indicating the chain is not available
- Node timeout or RPC error may return a 503 or gateway error
- Insufficient calldata may produce an incomplete simulation result
- Contract at target address may not be deployed on specified chain

## How this service works

Transaction pre-flight: will it revert (and why), gas, and which tokens/ETH move - before you send. Built for agents.

## Output

Returns whether the transaction will succeed or revert (with a decoded revert reason if applicable), a gas estimate, and a breakdown of all ERC-20 token transfers and ETH movements that would occur if the transaction were submitted.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string"
  },
  "data": {
   "type": "string"
  },
  "from": {
   "type": "string"
  },
  "block": {
   "type": "string"
  },
  "chain": {
   "type": "string"
  },
  "value": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/nodeflare-transaction-simulation-api-b423cdbc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from rpc.nodeflare.app](https://www.zero.xyz/host/rpc.nodeflare.app/llms.txt)