Base gas cost estimator API: swap fees under priority-fee scenarios

$0.01 per call · failed calls are never charged · no account or subscription: pay per call with a card key or USDC

Estimates Base gas costs from current fees and priority-fee presets. Fixed gas units (100k simple, 250k complex, 180k liquidity) are typical assumptions, not transaction-specific estimates or quotes. Valid values: standard, high-mev (3x priority fee), low-gas (half); invalid values return HTTP 400 without charge. No transaction simulation, mempool observation, or MEV/sandwich-risk measurement. Use to budget gas for a Base transaction.

When to use it

Run it free (25 free calls) Buy credits by card (from $1) Example result (JSON)

Try it with your own inputs

One of standard, high-mev, low-gas (default: standard)

Uses one of your 25 free calls. Nothing is charged, and a call that fails is not counted.

Inputs

NameTypeDescription
scenariostringOne of standard, high-mev, low-gas (default: standard). One of: standard, high-mev, low-gas.

Request

Over HTTP, with a card key from /credits:

curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/mev-simulator?scenario=standard"

Or one of your 25 free calls, no key:

curl "https://tools.funwords.eu/mev-simulator?scenario=standard&trial=1"

Without a key, the same URL answers 402 Payment Required with x402 and MPP terms, so an agent with a wallet pays per call in USDC (Base, Polygon, Arbitrum or Solana over x402; Base or Tempo over MPP) and retries.

Example result

{
  "chain": "base",
  "scenario": "standard",
  "gasPrice": {
    "baseFeeGwei": "0.05",
    "priorityFeeGwei": "0.1",
    "maxFeeGwei": "0.15"
  },
  "estimatedCosts": {
    "simpleSwap": {
      "gasUnits": 100000,
      "costEth": "0.000015",
      "costUsd": "0.06"
    },
    "complexSwap": {
      "gasUnits": 250000,
      "costEth": "0.0000375",
      "costUsd": "0.16"
    },
    "addLiquidity": {
      "gasUnits": 180000,
      "costEth": "0.000027",
      "costUsd": "0.11"
    }
  },
  "scenarioNotes": [
    "Gas units use typical fixed assumptions (100,000 simple swap, 250,000 complex swap, 180,000 add-liquidity), not a transaction-specific estimate or quote.",
    "This preset uses the current priority fee without adjustment."
  ],
  "blockNumber": 18650000
}

From an AI agent (MCP)

Add the MCP server to Claude, Cursor or any MCP client. This tool is mev_simulator, and the first 25 successful calls are free:

https://tools.funwords.eu/mcp

Questions

Does it simulate my transaction?

No. Gas units are fixed typical assumptions (100k simple, 250k complex, 180k liquidity), not transaction-specific estimates; there is no mempool observation or MEV or sandwich-risk measurement.

What if the scenario is wrong?

Invalid values return 400 without charge.

How do I pay?

Each successful call costs $0.01; failed calls are not charged. The first 25 calls are free. Then pay with card credits (from $1; the key goes in an Authorization header or, for clients that can only fetch a URL, as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.

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