An MCP server for live Base gas data, paid per call in USDC over the x402 payment protocol. No API key and no account: the agent pays a fraction of a cent from a wallet you control.

It answers the questions an RPC call cannot: what a transaction costs in dollars, which chain is cheapest right now, whether gas is high or low, and which hours to avoid.

Tools

Tool	Price	What it returns
`get_base_gas`	~$0.002	Base fee, low/medium/high priority fees, and the cost of a transaction in USD, ETH and gwei. Optional `gasLimit`.
`compare_gas_costs`	~$0.01	The same transaction on Base, OP Mainnet, Arbitrum One and Ethereum, in USD, cheapest first. Optional `gasLimit`.
`get_gas_history`	~$0.01	Base gas over the last `hours` (default 24): min/max/average/median and whether gas is cheap, normal, expensive or flat now.
`get_cheapest_window`	~$0.02	From 7 days of history: hours to avoid, cheapest hour (UTC), and the saving in percent and USD.
`get_service_status`	free	Whether the service is up and how much history it has collected. Needs no wallet.

Prices are set by the endpoint and published in its OpenAPI document. Every paid result includes the settlement transaction hash.

gasLimit guide: 21000 ETH transfer (default), ~65000 ERC-20 transfer, ~85000 NFT mint, ~180000 Uniswap swap, ~1500000 contract deploy.

Safety

The server only ever pays one origin, set by you (BASE_GAS_ORIGIN, defaulting to the live base-gas-x402 API). No tool takes a URL, so text the model reads cannot redirect your wallet to another paid endpoint.
Per-payment cap. Any payment above MAX_USD_PER_CALL (default 0.05) is refused before anything is signed.
Payments are EIP-3009 authorizations: the wallet needs USDC only, no ETH.
Use a separate wallet holding a few dollars. The key is read from the environment to sign payments and is never logged or returned.

The paid data source is a companion project: base-gas-x402.

Installation

Requirements

Node.js 18 or newer (built-in fetch is required)
A Base mainnet wallet holding a little USDC (no ETH needed)

git clone https://github.com/memosr/base-gas-mcp.git
cd base-gas-mcp
npm install

Pass BUYER_PRIVATE_KEY through your MCP client's config (see below). The server does not read a .env file.

Or run the published package directly with npx base-gas-mcp (see the config blocks below).

Getting a buyer key

BUYER_PRIVATE_KEY is the private key of a Base mainnet wallet. Create a fresh wallet (for example in MetaMask, Coinbase Wallet, or with cast wallet new), export its private key, and fund it on Base with a few dollars of USDC.

Warning: this is a real private key that controls real funds. Use a separate, disposable wallet holding only small amounts. Never reuse a key from a wallet with significant funds, never commit it to git, and never paste it into chat. The server reads it only to sign payments and never logs or returns it.

Environment variables

Variable	Required	Description
`BUYER_PRIVATE_KEY`	Yes	32-byte hex private key (64 hex chars, `0x` prefix optional) of a funded Base mainnet wallet.
`MAX_USD_PER_CALL`	No	Refuse any single payment above this many USD. Default `0.05`.
`BASE_GAS_ORIGIN`	No	The only origin the server pays. Defaults to `https://base-gas-x402-production.up.railway.app`.
`BUILDER_CODE`	No	Base Builder Code attached to the payment payload for attribution. Defaults to `bc_lhfd8zad`.

Configuration

Claude Desktop

Add to claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json, Windows: %APPDATA%\Claude\claude_desktop_config.json), then restart Claude Desktop:

{
  "mcpServers": {
    "base-gas": {
      "command": "npx",
      "args": ["-y", "base-gas-mcp"],
      "env": {
        "BUYER_PRIVATE_KEY": "0xYOUR_FUNDED_BASE_MAINNET_PRIVATE_KEY"
      }
    }
  }
}

To run from a local clone instead, point command at Node and use the absolute path to the server:

{
  "mcpServers": {
    "base-gas": {
      "command": "node",
      "args": ["/absolute/path/to/base-gas-mcp/src/server.js"],
      "env": {
        "BUYER_PRIVATE_KEY": "0xYOUR_FUNDED_BASE_MAINNET_PRIVATE_KEY"
      }
    }
  }
}

Claude Code

claude mcp add base-gas \
  --env BUYER_PRIVATE_KEY=0xYOUR_FUNDED_BASE_MAINNET_PRIVATE_KEY \
  -- npx -y base-gas-mcp

Or from a local clone:

claude mcp add base-gas \
  --env BUYER_PRIVATE_KEY=0xYOUR_FUNDED_BASE_MAINNET_PRIVATE_KEY \
  -- node /absolute/path/to/base-gas-mcp/src/server.js

The server reads its settings only from the environment the client passes. It does not load a .env file (since 0.3.1), so a .env in whatever folder the client opens cannot change where the wallet pays.

Example usage

Once configured, ask your agent:

"What does a Uniswap swap on Base cost right now, in dollars?" (get_base_gas with gasLimit 180000)
"Is Base or Arbitrum cheaper for a token transfer at the moment?" (compare_gas_costs)
"Is Base gas high right now, or should I wait?" (get_gas_history)
"When should I schedule a batch of transactions on Base?" (get_cheapest_window)

Each of these is one paid call. Check get_service_status first for free.

Tech stack

Node.js (ESM), served over stdio transport
@modelcontextprotocol/sdk for the MCP server
@x402/fetch, @x402/evm, and @x402/extensions for the payment-wrapped fetch, the EIP-3009 exact payment scheme, and builder-code attribution
viem for account handling and signing
zod for input validation