Gas Estimator API

Multi-chain gas prices in one call -- ETH, Base, Polygon, Arbitrum, BSC. Compare chains to find cheapest. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

{
  "mcpServers": {
    "gas-estimator": {
      "url": "https://gas-estimator.api.klymax402.com/mcp"
    }
  }
}

Quickstart -- HTTP (x402)

curl -X POST "https://gas-estimator.api.klymax402.com/api/estimate" \
  -H "Content-Type: application/json" \
  -d '{}'
-> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

| Tool | Method | Path | Price | Description |
|---|---|---|---|---|
| crypto_estimate_gas | POST | /api/estimate | $0.002 | Get gas price estimates across multiple EVM chains with USD cost |

crypto_estimate_gas

Use this when you need to compare gas prices across multiple EVM chains at once. Returns multi-chain gas estimates in JSON.

Parameters

| Name | Type | Required | Description |
|---|---|---|---|
| chain | string | no | Chain name: ethereum, base, polygon, arbitrum, bsc. Omit for all chains. |

Returns

- chains -- array of chain gas data with chain name
- low -- gas price in gwei for slow confirmation
- medium -- gas price in gwei for standard confirmation
- high -- gas price in gwei for fast confirmation
- transferCostUsd -- estimated USD cost for a simple transfer on each chain
- cheapestChain -- which chain currently has the lowest gas cost

Example response:

{"chains":[{"chain":"base","low":0.005,"medium":0.008,"high":0.012,"transferCostUsd":0.01},{"chain":"ethereum","low":12.5,"medium":18.0,"high":25.0,"transferCostUsd":0.85}],"cheapestChain":"base"}

When to use: choosing the cheapest chain before a cross-chain transaction. Essential for multi-chain agents that need to optimize gas costs.

Not for: swap quotes (use dex_get_swap_quote), bridging (use bridge_find_best_route).

Example agent prompts

- "Compare gas prices across multiple EVM chains at once"

Payment

- Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key
- Network: Base L2 (eip155:8453)
- Asset: USDC
- Facilitator: Coinbase CDP (primary), PayAI (fallback)
- Also reachable via ATXP (OAuth-wrapped x402, RFC 9728 protected-resource metadata)

Part of klymax402

100 x402 micropayment APIs for AI agents -- one wallet, USDC on Base, zero signup.

- Catalog: https://klymax402.com/llms.txt
- Full API reference: https://klymax402.com/llms-full.txt
- Live stats: https://klymax402.com/stats

License

MIT