feat: Gas Estimation Agent for multi-chain cost comparison

[dagangtj]

Overview

This PR implements a Gas Estimation Agent that compares real-time gas costs across Tempo L1, Ethereum, Arbitrum, and Base, helping users choose the most cost-effective chain for their transactions.

Closes

Closes #7

Features

✅ Multi-chain support: Tempo L1, Ethereum, Arbitrum, Base
✅ Real-time gas prices in gwei and USD equivalent
✅ Cost estimation for common operations:

• Simple transfer (21k gas)
• ERC-20 transfer (65k gas)
• Contract deployment (1.5M gas)
  ✅ Smart recommendations for cheapest chain
  ✅ 15-second caching for performance
  ✅ RPC fallback handling for reliability

Example Response

{
  "operation": "ERC-20 Transfer",
  "estimates": [
    {"chain": "Tempo L1", "gasPrice": "0.00 gwei", "cost": "$0.0000", "speed": "1s"},
    {"chain": "Base", "gasPrice": "0.02 gwei", "cost": "$0.0039", "speed": "2s"},
    {"chain": "Arbitrum", "gasPrice": "0.05 gwei", "cost": "$0.0098", "speed": "2s"},
    {"chain": "Ethereum", "gasPrice": "25.00 gwei", "cost": "$4.8750", "speed": "12s"}
  ],
  "recommendation": "Tempo L1 has zero gas fees with fast finality (1s). Highly recommended for cost-sensitive operations."
}

Acceptance Criteria

All requirements from issue #7 fulfilled:

• ✅ Queries gas prices from 4+ chains (Tempo, Ethereum, Arbitrum, Base)
• ✅ Returns gas costs in native units (gwei) and USD equivalent
• ✅ Estimates cost for common operations (transfer, ERC-20, deploy)
• ✅ Provides recommendation for cheapest chain
• ✅ Caches results with configurable TTL (default 15s)
• ✅ Handles RPC failures gracefully with fallbacks
• ✅ Registers on PayPol marketplace via SDK

Testing

cd agents/gas-estimator
npm install
npm run dev

Test endpoints:

• GET /health - Health check
• GET /manifest - Agent metadata
• POST /execute - Run gas estimation

Implementation Details

• RPC providers: Public endpoints with fallback support
• Caching: 15-second TTL to reduce RPC calls
• Error handling: Graceful degradation on RPC failures
• Price oracle: ETH/USD price for cost calculations
• TypeScript: Full type safety with ethers.js v6

Files Changed

• agents/gas-estimator/src/index.ts - Main agent logic
• agents/gas-estimator/src/register.ts - Marketplace registration
• agents/gas-estimator/package.json - Dependencies
• agents/gas-estimator/README.md - Documentation
• agents/gas-estimator/.env.example - Configuration template