gate402-mcp

MCP server for Gate402 — pay-per-call agent APIs over HTTP 402 (x402 / USDC on Base). Gives any MCP client four tools with no signup and a free tier on first runs:

…plus three free tools that run locally in this process (pure compute — no payment, no key, no network):

How billing works

On first use the server self-claims a free-credit API key from Gate402 and caches it at ~/.gate402-mcp/key.json. Calls draw down that credit. When it runs out, tools return a top-up link instead of failing. To skip the free tier, set GATE402_API_KEY to a funded account (top up).

The payment is the auth — there are no accounts to create.

Install

npm install -g gate402-mcp

Or run without installing via npx gate402-mcp.

Configure your MCP client

Claude Desktop / Claude Code

Add to your MCP config (claude_desktop_config.json, or claude mcp add):

{
  "mcpServers": {
    "gate402": {
      "command": "npx",
      "args": ["-y", "gate402-mcp"]
    }
  }
}

Cursor / Cline / Windsurf

Same shape — point the MCP server command at npx -y gate402-mcp.

Agent frameworks (LangChain, CrewAI, LlamaIndex)

gate402 is a standard stdio MCP server, so any framework with an MCP adapter can load all 11 tools:

LangChain / LangGraph (langchain-mcp-adapters):

from langchain_mcp_adapters.client import MultiServerMCPClient
client = MultiServerMCPClient({"gate402": {"command": "npx", "args": ["-y", "gate402-mcp"], "transport": "stdio"}})
tools = await client.get_tools()   # feed into your agent

CrewAI (MCPServerAdapter):

from crewai_tools import MCPServerAdapter
from mcp import StdioServerParameters
params = StdioServerParameters(command="npx", args=["-y", "gate402-mcp"])
with MCPServerAdapter(params) as tools:
    ...  # pass tools to your Crew

LlamaIndex (McpToolSpec):

from llama_index.tools.mcp import BasicMCPClient, McpToolSpec
tools = McpToolSpec(client=BasicMCPClient("npx", args=["-y", "gate402-mcp"])).to_tool_list()

Once wired, the agent calls the tools autonomously; the free-credit key is claimed on first use, and paid tools draw down from it.

Environment variables

Develop

npm install
npm run build
npm start          # or: npm run dev

License

MIT