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Just transaction simulation, as a no-account API
Tenderly is a full simulation, debugging and monitoring platform. If all you need is the pre-flight — will this tx revert? how much gas? which assets move? — NodeFlare gives you exactly that as an API across all 23EVM chains, including the young chains Tenderly doesn't cover. No account for the basics; pay per call in USDC over x402, or use a free key.
Honest scope:this replaces Tenderly's transaction-simulation use case, not the whole platform. Need deep debug traces, production monitoring or virtual testnets? Tenderly does more. Need a fast, account-free reverts / gas / asset-changescheck from a backend or an agent, on more chains? That's this.
Tenderly vs NodeFlare (for simulation)
| Dimension | Tenderly | NodeFlare |
|---|---|---|
| Scope | Full platform: simulation + debugging + monitoring + alerts + virtual testnets | Just tx pre-flight simulation: reverts / gas / asset changes |
| Access | Account + dashboard; API keyed to a project | No account for the public tier; free key or x402 pay-per-call |
| Simulation output | Rich trace, state diffs, decoded calls | Reverts (+ reason), gas estimate, and per-asset in/out changes |
| Chain coverage | Majors and many EVM chains | All 23, including young chains (Robinhood, Plasma, Ink, Zircuit) Tenderly doesn't cover |
| Built for | Dev teams debugging + monitoring in a UI | Backends and AI agents pre-flighting a tx before signing |
Pre-flight a tx in one call
# Pre-flight a transaction before signing (public tier: reverts + gas)
curl -X POST https://rpc.nodeflare.app/data/simulate \
-H 'Content-Type: application/json' \
-d '{
"chain": "base",
"from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
"to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"data": "0xa9059cbb..."
}'
# → { "reverts": false, "gasEstimate": { "decimal": "51234", "hex": "0xc822" } }
# Add asset-change tracing (which tokens move in/out) — pay per call, no account
curl -X POST https://rpc.nodeflare.app/data/simulate/x402 \
-H 'Content-Type: application/json' \
-d '{ "chain": "eth", "from": "0x...", "to": "0x...", "data": "0x..." }'
# → also returns "assetChanges": [ { token, symbol, direction, amount } ]Why NodeFlare for pre-flight
No account, pay-per-call
Public tier for reverts + gas with no signup; asset-change tracing over x402 in USDC — no seat, no subscription.
Young chains covered
Simulate on Robinhood Chain, Plasma, Ink, Zircuit and more — chains where no third-party simulator exists at all.
Agent-native
simulate_transaction is an MCP tool and an x402 endpoint — an execution agent pre-flights every tx and pays per call.
Transaction simulation — FAQ
Is NodeFlare a full Tenderly replacement?
No — and it doesn't pretend to be. Tenderly is a whole platform: simulation, transaction debugging, monitoring, alerting and virtual testnets, in a dashboard. NodeFlare covers one slice of that — transaction pre-flight simulation — as a lightweight, no-account API. If you need deep debugging traces, production monitoring or testnet forks, Tenderly does far more. If all you need is "will this tx revert, what gas, which assets move?" from a backend or an agent, NodeFlare is a faster, account-free way to get it across more chains.
What does /data/simulate return?
On the public tier: whether the transaction would revert (with the revert reason or selector when available) and a gas estimate. On the paid tier it adds asset-change tracing — which tokens and how much move into and out of the from address if the tx executes. Pass chain, from, to, data (and optional value); you get the pre-signature answer an agent needs to avoid burning gas on a doomed or malicious call.
Which chains can I simulate on?
All 23 EVM chains NodeFlare serves — the majors (Ethereum, Base, BNB Chain, Arbitrum, Optimism, Polygon) plus young chains like Robinhood Chain (4663), Plasma, Ink and Zircuit where no third-party simulator exists at all. Asset-change tracing needs debug/trace support on the chain; where it's unavailable the response says so and still returns reverts + gas.
Do I need an account or API key?
Not for the basic simulation — the public /data/simulate endpoint returns reverts + gas, rate-limited per IP, no signup. Asset-change tracing uses heavier methods, so it runs on a free NodeFlare API key or over x402 (append /x402) with pay-per-call in USDC and no account.
Can an AI agent call it?
Yes — it's the simulate_transaction tool in the NodeFlare MCP server (npm nodeflare-mcp and mcp.nodeflare.app/mcp) and an x402 pay-per-call endpoint. A trading or execution agent can pre-flight every transaction and pay per call in USDC with no account.
Related
- The full Agent Intelligence API → — balances, portfolio, approvals, simulation, wallet reports, token safety
- Token Safety API → — screen a token for scam / honeypot risk before you transact
- MCP for AI agents → — simulate_transaction as a tool in Claude, Cursor, ChatGPT
Pre-flight every transaction
The public simulation endpoint works today — no signup. Add a free key or x402 for asset-change tracing.