Use 402.report with LangChain.js

LangChain.js consumes MCP servers through @langchain/mcp-adapters. 402.report exposes your x402 spend + forensics as read-only MCP tools your agents can call.

1. Install

npm install @402report/sdk @langchain/mcp-adapters

Set your key as REPORT402_API_KEY (create one in the dashboard).

2. Load the spend tools

import { MultiServerMCPClient } from "@langchain/mcp-adapters";
import { mcpHttpConfig } from "@402report/sdk";

const { url, headers } = mcpHttpConfig({ apiKey: process.env.REPORT402_API_KEY! });

const client = new MultiServerMCPClient({
  mcpServers: {
    report402: { transport: "http", url, headers },
  },
});

const tools = await client.getTools();
// Pass `tools` to a LangGraph/LangChain agent (e.g. createReactAgent({ llm, tools })).

3. Observe the payments your agent makes

Route outbound HTTP through the proxy so x402 activity is recorded. Anywhere your tools call a paid API with fetch, use the proxy fetch:

import { createProxyFetch } from "@402report/sdk";

const fetch402 = createProxyFetch({ apiKey: process.env.REPORT402_API_KEY! });
const res = await fetch402("https://api.example.com/premium");

402.report is non-custodial — it observes x402 activity, it never holds or settles funds.