@agenticpay/mcp-bridge

A real MCP server (stdio transport, @modelcontextprotocol/sdk) that exposes x402-paywalled HTTP endpoints as MCP tools. Drop into Claude Desktop, Cursor, Continue.dev, or any MCP client.

The bridge holds a Solana keypair, signs each x402 payment payload, and settles via a facilitator on the agent's behalf. The MCP client sees normal MCP tools — it never touches the payment plumbing.

Why this exists

@agenticpay/mcp-server is the resource server (the place that wants to get paid). @agenticpay/mcp-bridge is the client adapter that makes those paid endpoints appear as native MCP tools to AI clients that already speak MCP.

Use case: you want Claude Desktop to be able to call paid APIs without managing wallets or signing payments yourself. The bridge handles it.

Install / use with Claude Desktop

// ~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "agenticpay": {
      "command": "npx",
      "args": ["-y", "@agenticpay/mcp-bridge"],
      "env": {
        "AGENTICPAY_BRIDGE_KEYPAIR": "[12,34,...your 64-byte keypair]",
        "AGENTICPAY_BRIDGE_NETWORK": "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
        "AGENTICPAY_BRIDGE_RPC": "https://api.devnet.solana.com",
        "AGENTICPAY_BRIDGE_TOOLS": "[{\"name\":\"reverse_string\",\"description\":\"Reverse a string. Costs 0.001 USDC.\",\"url\":\"http://localhost:4021/tools/reverse\",\"inputSchema\":{\"text\":{\"type\":\"string\"}}}]"
      }
    }
  }
}

Restart Claude Desktop. The agenticpay tools (e.g. reverse_string) appear in the conversation. Claude calls them; the bridge pays, settles, returns the result.

Spend caps

The bridge signs payments autonomously, so cap what it may spend. Both caps are expressed in base units of the payment asset (USDC has 6 decimals, so "1000" = 0.001 USDC):

"env": {
  "AGENTICPAY_BRIDGE_MAX_PER_CALL": "5000",
  "AGENTICPAY_BRIDGE_SESSION_BUDGET": "100000"
}

• AGENTICPAY_BRIDGE_MAX_PER_CALL — refuse any single payment above this amount (here: 0.005 USDC).
• AGENTICPAY_BRIDGE_SESSION_BUDGET — refuse payments once the bridge process's cumulative spend would exceed this amount (here: 0.10 USDC). Counted when a payment is signed, so a settlement that later fails still consumes budget.

A refused payment surfaces to the MCP client as a tool error — the wallet is never touched. Programmatic equivalents: maxPaymentPerCall and sessionBudget in BridgeConfig.

Programmatic use

import { createBridge } from "@agenticpay/mcp-bridge";
import { z } from "zod";

await createBridge({
  keypairBytes: [12, 34, /* ... 64 bytes */],
  network: "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
  rpcUrl: "https://api.devnet.solana.com",
  tools: [
    {
      name: "reverse_string",
      description: "Reverse a string. Costs 0.001 USDC.",
      url: "http://localhost:4021/tools/reverse",
      inputSchema: { text: z.string() },
      formatResult: (body) => (body as { result: string }).result,
    },
  ],
});

Funding the bridge wallet

The wallet pays USDC for every tool call. Devnet:

• SOL: https://faucet.solana.com
• USDC: https://faucet.circle.com (Solana Devnet)

The facilitator (e.g. our hosted devnet endpoint) covers SOL gas — the bridge wallet only needs USDC.

Status

Pre-alpha. Devnet-validated. Mainnet works once you fund the wallet with real USDC and point at a mainnet-capable facilitator.

MIT licensed. See agenticpay monorepo.