POST /api/gas-estimate

Estimates the gas cost for a contract interaction on Mantle Sepolia. Queries the live RPC for eth_gasPrice and eth_estimateGas, then optionally enriches the response with AI-generated gas optimization suggestions.

---

Endpoint

POST /api/gas-estimate

Runtime: Node.js
Auth: Not required

---

Request

Body

{
  "address": "0x9d9b602CFe69cfF9706EAc399808E84682ce94FB",
  "calldata": "0x8456cb59",
  "from": "0x0000000000000000000000000000000000000001"
}

Parameter	Type	Required	Description
address	string	Yes	Target contract address (42-char hex)
calldata	string	Yes	Transaction calldata (hex, starts with 0x)
from	string	No	Sender address for gas estimation context

Validation

• address must match /^0x[0-9a-fA-F]{40}$/
• calldata must match /^0x[0-9a-fA-F]*$/
• Returns 400 if validation fails

---

Response

Success (200)

{
  "estimatedGas": 45000,
  "gasPriceGwei": 0.02,
  "estimatedCostMNT": "0.0000009000",
  "estimatedCostUSD": "0.00000072",
  "optimizations": [
    "Use uint256 instead of smaller integer types to avoid packing overhead in storage",
    "Cache storage variables in memory at the top of hot functions",
    "Emit events instead of storing non-critical data on-chain"
  ],
  "summary": "Estimated 45,000 gas units at 0.0200 Gwei on Mantle Sepolia. Apply the suggestions below to reduce execution cost."
}

Response Fields

Field	Type	Description
estimatedGas	number	Estimated gas units for the transaction
gasPriceGwei	number	Current gas price in Gwei (from eth_gasPrice)
estimatedCostMNT	string	Estimated cost in MNT (18 decimal places)
estimatedCostUSD	string	Approximate USD cost (MNT at ~$0.80)
optimizations	string[]	3 AI-generated gas optimization suggestions
summary	string	Human-readable cost summary

Error: Gas Estimation Failed (422)

{
  "error": "Gas estimation failed: execution reverted. The transaction may revert or require a specific caller.",
  "gasPriceGwei": 0.02
}

Returns the current gas price even when estimation fails.

Error: Invalid Input (400)

{
  "error": "Invalid contract address."
}

---

How It Works

Step 1: Get Current Gas Price

const gasPriceHex = await rpcCall('eth_gasPrice', []);
const gasPriceWei = parseInt(gasPriceHex, 16);
const gasPriceGwei = gasPriceWei / 1e9;

Step 2: Estimate Gas

const estimateHex = await rpcCall('eth_estimateGas', [{
  to: address,
  data: calldata,
  from: from ?? '0x0000000000000000000000000000000000000001',
}]);
estimatedGas = parseInt(estimateHex, 16);

If eth_estimateGas reverts (transaction would fail), returns 422 with the error message and current gas price.

Step 3: Calculate Cost

const costWei = BigInt(estimatedGas) * BigInt(gasPriceWei);
const costMNT = Number(costWei) / 1e18;
const costUSD = costMNT * 0.80;  // Approximate MNT/USD

Step 4: AI Optimization Suggestions

An optional AI call generates gas optimization tips:

async function callAI(estimatedGas: number, calldata: string, address: string) {
  const prompt = `A developer is calling a smart contract on Mantle Sepolia (EVM L2):

Contract address: ${address}
Calldata: ${calldata.slice(0, 200)}
Estimated gas: ${estimatedGas.toLocaleString()} units

Provide 3 specific, actionable Solidity gas optimization suggestions that could reduce this gas cost. Focus on Mantle L2 specific optimizations and general EVM best practices.

Return only a JSON array of strings: ["<opt 1>", "<opt 2>", "<opt 3>"]`;

  // Try Hunyuan first, then Groq
  if (process.env.HUNYUAN_API_KEY) {
    const res = await fetch('https://api.hunyuan.cloud.tencent.com/v1/chat/completions', {
      model: 'hunyuan-lite',
      messages: [
        { role: 'system', content: 'You are an EVM gas optimization expert. Return only valid JSON arrays. No markdown.' },
        { role: 'user', content: prompt }
      ],
      temperature: 0.2,
      max_tokens: 400,
    });
    // ...
  }

  if (process.env.GROQ_API_KEY) {
    const res = await fetch('https://api.groq.com/openai/v1/chat/completions', {
      model: 'llama-3.1-8b-instant',
      messages: [
        { role: 'system', content: 'You are an EVM gas optimization expert...' },
        { role: 'user', content: prompt }
      ],
      temperature: 0.2,
      max_tokens: 400,
      response_format: { type: 'json_object' },
    });
    // Groq json_object may return { optimizations: [...] } or just [...]
    const arr = Array.isArray(parsed) ? parsed : (parsed.optimizations ?? []);
  }
}

Fallback Optimizations

If no AI provider is available:

const FALLBACK = {
  estimatedGas: 45000,
  gasPriceGwei: 0.02,
  estimatedCostMNT: '0.0000009',
  estimatedCostUSD: '0.00000072',
  optimizations: [
    'Use uint256 instead of smaller integer types to avoid packing overhead in storage',
    'Cache storage variables in memory at the top of hot functions',
    'Emit events instead of storing non-critical data on-chain',
  ],
  summary: 'This is a standard operation. Savings are possible by reducing storage writes and using packed structs where applicable.',
};

---

Mantle Sepolia Gas Characteristics

Mantle Sepolia is an Optimism-based L2 with very low gas costs:

Parameter	Typical Value
Gas price	~0.02 Gwei
L1 data fee	Included in gas price
Block time	~2 seconds

At 0.02 Gwei, a 120,000 gas transaction costs approximately 0.0000024 MNT (~$0.00000192 USD).

---

Example: cURL

curl -X POST http://localhost:3000/api/gas-estimate \
  -H "Content-Type: application/json" \
  -d '{
    "address": "0x9d9b602CFe69cfF9706EAc399808E84682ce94FB",
    "calldata": "0x8456cb59"
  }'

Response

{
  "estimatedGas": 28734,
  "gasPriceGwei": 0.020018,
  "estimatedCostMNT": "0.0000005749",
  "estimatedCostUSD": "0.00000046",
  "optimizations": [
    "Use uint256 instead of smaller integer types...",
    "Cache storage variables in memory...",
    "Emit events instead of storing..."
  ],
  "summary": "Estimated 28,734 gas units at 0.0200 Gwei on Mantle Sepolia. Apply the suggestions below to reduce execution cost."
}

---

Performance

Stage	Typical Latency
eth_gasPrice RPC call	50-150ms
eth_estimateGas RPC call	100-300ms
AI optimization suggestions	200-800ms
Fallback	<5ms
Total (with AI)	350-1250ms
Total (fallback)	150-450ms

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Next Steps

• Analyze Threat -- AI threat classification for suspicious transactions
• Sentinels API -- Manage monitored protocol contracts