# Synapse API — Ethereum Gas Estimator

> Synapse API — Ethereum Gas Estimator is a paid API for AI agents from synapse-api-brown.vercel.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-11).

Estimates the gas cost for an Ethereum transaction given sender, recipient, value, and calldata

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/ethereum/gas/estimate?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-ethereum-gas-estimator-acb46008
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BmwntDTWToV6v2S_AuJrO

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 synapse-api-ethereum-gas-estimator-acb46008 -d '<json body>'
```

Example prompt: Estimate how much gas it will take to send 0.5 ETH from 0xAbC...123 to 0xDeF...456 with no extra calldata — I want to know the gas units before I submit the transaction.

## When to prefer this

Use this endpoint when you need a quick, pay-per-call Ethereum gas estimate without running your own Ethereum node or maintaining an RPC subscription. It is ideal for AI agents that need to pre-validate transaction costs before submission, especially in workflows that span 57+ blockchain networks via the same Synapse API suite.

## Known failure modes

- Invalid Ethereum address format for 'to' or 'from' fields — returns 4xx error
- Malformed or non-hex calldata in 'data' field — returns parsing error
- Simulated transaction reverts on-chain — may return revert reason or error code
- Service unavailable or Ethereum node connectivity issues — returns 5xx error
- Missing required fields — may return validation error or default estimate

## How this service works

High-speed API suite for AI processing, web scraping, and smart data utilities across 57+ blockchain networks. Pay-per-call via x402.

## Output

Returns an estimated gas amount (in gas units) required to execute the described Ethereum transaction. The response allows developers and agents to set appropriate gas limits before broadcasting a transaction on-chain.

## Request schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synapse-api-ethereum-gas-estimator-acb46008/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from synapse-api-brown.vercel.app](https://www.zero.xyz/host/synapse-api-brown.vercel.app/llms.txt)