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"
    }
  }
}

Related MCP server: base-gas-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

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

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